A. Substance1

The category.

All existents, being complexes of space—time, are substances, because any portion of Space is temporal or is the theatre of succession; or what is the same thing because all succession is spread out in space. In other words, spaces and durations are not themselves substances as if substance were a notion anterior to them and applied to them; but because Space-Time is what it is, and every space is a duration and every duration an extension in space, substance is a determination of all things which occupy Space and Time. We are introduced here to a category which arises not so much out of the character of spatio-temporality taken as a whole given entity as out of the ‘relation’ (if we may misapply a word strictly applicable only to pieces of Space-Time2) between the spatial and the temporal elements in any space-time. For simplicity and brevity it will be enough to speak of substance as a piece of Space which is the scene of succession without stating the same thing in terms of Time, in the reverse order. Any existent is a substance in this account of the matter. Even a simple motion in a straight line is an extreme instance of the life of a substance, though the motion be not repeated and the substance endures or remains identical only for the duration of the single motion.

But it will be easier to deal first with what are ordinarily called things which possess many qualities connected together, and to consider simpler substances in the light of the more complex ones. Qualities it is assumed are correlated with certain motions; and it is indifferent for our purpose whether the quality belongs, as will be here maintained, to the motion itself; or belongs to mind and is the mental correlate of the motion, as is the belief of those who distinguish primary from secondary qualities, but recognise a primary correlate of the secondary quality. A thing or complex substance is then a contour of space (i.e. a volume with a contour) within which take place the motions correlated to the qualities of the thing; and the complex substance or thing is the persistence in time of this spatial contour with its defining motions. Thus movements correlated with the quality yellow and others correlated with the quality hard are contained within the contour of the atom or molecule of gold. Within the contour the qualities are grouped according to the law of the construction of the substance. The various movements which constitute what has been before called that ‘configuration’ of space-time which the thing is, define a certain outline of space, that is, a certain volume of space with its outline. As Time moves on the substance may change in its characters or in the relation of them one to the other but always within the limits set by the law of its construction. Our most easily understood example of substance is found in our own mind. There the activities of mind change from one moment to another according to the objects which engage it. Sometimes indeed the consciousness located in one portion of the extended mind lapses into unconsciousness. But always we have under the various changes in the distribution of our attention in Time the same relative configuration of movements within the total outline occupied by our minds. It is the persistence of this including space throughout a lapse of time, a persistence which means, as we have seen in our original account of Space-Time, a ceaseless redistribution (in the form of motions) of instants of time amongst points of space, which makes our minds a substance and a substantial identity. Or we may take as another instance an organism with different activities in different parts of the structure, all these activities constituting a configuration of space-time bounded within the space of the organism. Or we may, as on previous occasions, consider the organism as a substance from the point of view of the changing distribution in the maturity of its cells.

The persistence of a piece of Space in Time which results from the retention of the configuration of its movements according to its law of construction does not of course imply that the piece of Space is stationary as a whole. On the contrary, no substance occupies the same place continuously, if only because of the movement of the earth or other heavenly body, and it may change its place also by locomotion or transference. But the contour and internal configuration remain within limits the same, though not the position of the whole thing.

The movements underlying qualities may be complex and the configuration of a thing with qualities is undoubtedly very complex. In a simpler substance such as a vibratory movement which has the quality sound, the excursion of the vibration fills and defines a certain contour of space and a comparatively simple one. When we come to the simplest substance of all, the life of which is movement in a straight line, what we have is the occupation of the most elementary contour in space, viz. a point by an instant in time. To understand such simplicity we had first to understand the nature of more complex substances. It might be thought that the whole excursion of the point was the contour of the substance. But in fact the sweep of the movement is comparable to the translation of our mind (or say our body) as we move; only that in the simpler case the translation is the very essence of the life of the point whereas the essence of the life of the mind as mind is in the movements which take place within the mind's spatial contour. For the point-instant is of itself motion, it is the element of motion. A point is not a stable or fixed thing but in virtue of its time is connected with some other point-instant. The meaning of motion is, as was noted before, not that the point of space itself moves as if it were a material body-shifting its place, but that the time of a point ceases to be present, and the present is transferred to another point continuous with it. That is to say, the contour of the substance remains the same as the original point. The simplest substance is consequently a movement. When we take this movement in its limiting form we have the point-instant, which may thus be called a momentary substance. For a point-instant is by its very nature a movement, not something statical. It is an ideal, not an actual movement; and just for this reason it is the actual elementary existent, and is real just in virtue of its ideal character.3 The conception of substance at this limit, at which it becomes momentary, is hardest to grasp, and I may add rewards most when it is grasped.

Identity of substance.

The identity of a substance is individual identity as persisting through a duration of time. Numerical identity was occupation of a point-instant or complex of them. Generic identity or identity of sort was the preservation of a plan of construction throughout repetition at different times or places. When the repetition of a plan is found in its varying phases in the duration of an individual we had individual identity. We see now that substantial identity is equivalent to individual identity. Before, under individual identity we were thinking of the universality of the plan or a particular in respect of the moments of its life. The notion of substantial identity represents these moments as woven together through the constant changes of its internal motions in accordance with a plan of construction. Individuality regards the repeated plan; substantial identity the persistence of the particularised universal or individual through a period of time. In practice substantial identity and individuality are the same conception; and by the individuality of a thing is meant in general its identity of substance. This combines then the two elements of repetition of a plan with persistence of the contour of space within which the motions take place which obey the plan. Personal identity is a special instance of substantial identity. It means the coherence of our mental life within an extension which is occupied variously through the changing moments of our life. Only since the enjoyed spatial extension of our mind is overlooked we are apt to think of it as merely coherence in time, as if there could be such coherence except for the space which establishes it. In all cases it is the spatial contour which provides the unity of substance, that spatial extent being itself meaningless without motions to occupy it, that is without persistence in time.4

What changes are compatible with the retention of substantial identity is an empirical question which can only be decided by reference to each case or kind of cases. In the first place, it does not follow that qualities are always localised in the same part of the volume of the space or substance, though this appears to be the case with minds where the kinds of consciousness corresponding to certain objects are more or less definitely restricted in locality. Even organic bodies may change colour in different places as when we blush, or as in the crustaceans before mentioned which change their colour with the time of day. Under this head would come the famous question of Sir John Cutler's stockings which had been so darned with green silk that not a thread of the original black silk was left. Were the stockings the same or not? It would seem to be the case that though the stockings were not in the end of the same material the configuration of the motions within the substance had been preserved. In the all-important matter the substance had not ceased to be a stocking and retained its empirical identity.

In the second place, the contour itself may vary within limits without destroying the constructive plan, and so far as this is the case the identity of substance remains. The main distinction of aggregates and organised beings lies in this, that an aggregate may be diminished without essential alteration, except naturally of those characters which depend on the aggregation as such, e.g. magnitude of the substance or strength of the material. This is because the components of such secondary substances are alike. Even here if a block of marble is chipped it is difficult, if the process of chipping continues long enough, to call the remainder the same marble; there is only a piece of it, the substance remains the same only generically. Organisms grow, and parts may be removed, it is found in experience, without destroying the identity of the substance, though the contour may be much altered, as by the loss of a limb. Everything depends on the importance of what is lost for the plan of the whole. We can only note these limits as they occur in experience. A man may lose a leg and not be much altered, while an atom may lose two alpha particles and become a different chemical body.

The empirical questions as to the preservation of the identity of mind and how, when it is ruptured, it may be revived, questions which have already been hinted at, will meet us again at a later stage of the inquiry. Another question belongs entirely to a later stage, and that is the relation of a thing or substance to its appearances; which of its appearances belong to the thing itself, which are mere appearances and imply something else in addition. This question, as indicated by the word appearance, concerns the connection of a thing with the mind or other ‘percipient’ and belongs to the empirical relations of things.5 Here we have considered substance, as a union of qualities, as it is in itself.

That unity then is supplied by the space (that is the space-time) within which the qualities are disposed. Each quality inheres in the substance because it is included in the space which unifies the substance. Thus the proposition, this sugar is sweet, means that the universal sweet in an individualised shape, that is as a definite and particular motion, is found within the volume of the sugar. There is a complete difference between such a proposition and one in which the predicate is the class-concept of the thing, e.g. this is sugar, where the predicate is the total plan of configuration which determines the contour of the space of the substance.

Qualities do not interpenetrate.

A conclusion of some importance seems to be implied in this conception of substance. Not only is the inherence of the sweetness and the whiteness merely the fact that the motions correspondent to these qualities occur within the contour of the substance, but these motions occur in different places. The qualities of a substance do not interpenetrate. It can only be supposed that they do, if qualities are treated as mental creations or ideas and, because they are such, are somehow regarded as not being in space or time. But the motions at any rate which correspond to the qualities are separate from one another and differently located. They seem to interpenetrate only because not distinguished in our apprehension. The motion of whiteness (which for us is white) may to our coarse apprehension be in the same place as the sweetness; and we may say the sugar is white and sweet all over. But two different motions, when not compounded into a single-resultant motion, do not occupy precisely the same place. One may take place in the interstices of the other, as it were, and be indistinguishable for us in locality. When a body is sweet and white all over, the motions of whiteness and sweetness are repeated in various places and intermixed, as blue and red points of colour may be dotted over a page one set among the other. The motions of white are spread over the volume like stippled points in an engraving and the sweetness motions among them. Just as blood is seen uniformly red though only the red corpuscles in it are red, so the sweet and white stippling gives the impression (through different senses) of a uniformly sweet white thing.6

Thus a substance in respect of its qualities may be described as a space of a certain contour stippled over with qualities. There is no pretence of any mysterious support of qualities, such as Berkeley shrunk from and thought to be a “brute senseless somewhat.” The support of qualities is nothing more nor less than the space-time within whose spatial contour they are united, they themselves being parts of the space, whose contour their configuration defines. For though we have spoken mainly for convenience of the space-contour, yet remembering that substance is persistence of this spatial contour through time, each moment of the substance being a particular of which the law of configuration is the universal (the singular universal), we must think of substance as a specially defined volume of space-time. The substance may be material or mental or living. But ultimately the substantiality of it is its defined volume of space-time.

Connection of qualities.

Within this volume the motions to which qualities belong are, primarily speaking, juxtaposed. But their relation is more than is expressed by the somewhat depreciatory name of juxtaposition. One of the great difficulties that have been felt as to the reality of substance is that it appears to be a mere aggregate of qualities. Sugar is sweet and white and hard and the like. But Space and Time are continuous, and to be within a volume of space-time is to be connected by a space-time. And in saying this we need take no account of the purely empirical fact that within a substance which is compound there may be empty space-times or pores not included in the substance itself. How far the empty space-time, empty that is of qualities, belongs to the substance or not is an empirical affair. The space-time within which the electrons of the atom are supposed to circle about their nucleus, is perhaps not a pore in the substance but part of it, just as are the interstellar spaces of the solar system. On the other hand, the pores in a sponge do not belong to the substance of the sponge.

Now the space-time within which the motions are found which have their qualities (if they have any) makes these qualities into a continuum. Such an answer is sufficient. But more exact and explicit description of their connection is desirable. To supply this is a difficult matter, but it must be attempted. We have first to refer back to the general account of Space-Time. Structure we saw was provided for by the fact that any instant is repeated in Space, and there is therefore intrinsic simultaneity of certain points. Now given this fundamental connection as a basis, different lines of advance from it will leave us with events in the substance which are simultaneous with one another though of different qualities. Thus at least a whiteness and a sweetness condition of the substance may co-exist, not in virtue of a direct connection between whiteness and sweetness but as the joint outcome of processes beginning with the primordial connection. Qualities would on this showing be connected together by a remoter relation. This corresponds to the familiar (Lockeian) notion that the various qualities of a substance are traceable to the nature of the primary qualities of their primitive constituents. The correspondence is of course not exact but on the contrary very inexact. But it consists in this, that the multiplicity of properties of a substance is not haphazard but rooted in some simple state of affairs which enables many qualities to belong together within one contour and to be in part simultaneous. For though any substance is, like the universe as a whole, doing its work at different times in its different parts when considered with reference to some point-instant of it, there must be structure and simultaneity for it to be a substance at all. (This statement includes at the limiting case a simple movement.) A body, for instance, could not be dying all at once in every cell if it is to be a continuous structure. It was only the gradual darning of the black silk stockings with green silk which prevented them from being another pair of stockings. It is of course empirical what original movements are provided for in the substance. But an empirical connection is not the same thing as a purely haphazard one of mere juxtaposition.

But besides the remoter connection of organised movements, with their qualities, there is also the direct interconnection of qualities or movements such as is illustrated for us in the mutual support of the functions of an organic body by one another, the sustainment of nervous action, for instance, by nutrition, and the regulation of nutrition by nervous action. Here we have reciprocal action of different substances within the whole substance. This reciprocity means causal relation within the substance and is only possible through the connecting space-time. Reciprocity we propose to discuss presently. Now reciprocal actions are at a certain instant of time simultaneous; and so far as there is mutual interaction between movements within a substance there is a more special simultaneity of events within it.

On both grounds we are able to understand, though I confess the matter is difficult and the account given of it inadequate, how a substance can have many qualities at the same time. The connection in whatever form is a spatio-temporal one.

B. Causality

The category.

Space-Time or the system of motion is a continuous system, and any motion within it is continuous with some other motion. This relation of continuity between two different motions is causality, the motion which precedes that into which it is continued in the order of time being the cause and the other the effect. Motion, like murder, will out, and no motion is indifferent to other motions within the universe. Thus the contraction of certain muscles in a boy's hand and arm is transformed into or continued into or replaced by certain intramolecular movements in a stone which constitute a translation of the stone at a certain velocity; this motion is transformed into the shattering of the window which the stone strikes. A blow from a bullet on a target is transformed into motions in the target which constitute a dent in it. An electric stimulation of a nerve ending is transformed into a movement up the nerve (I will not attempt to characterise the intimate nature of the movement, which is of a highly complicated sort) which ends ultimately in a sensation, which is itself a movement (or is correlated with one). A dose of digitalis so affects the pneumogastric nerve as to end in a cessation of the heart's action, which is equivalent to a new set of intramolecular movements in the heart and is not a bare negative, but only a negative of its previous actions. The motion of light, that is a motion of a complex sort in the supposed ether, at any rate the motion belonging to that substance which is light, is transformed into certain motions in a photographic plate, of a chemical order.7

Causality and Substance.

It is immaterial, with our metaphysical conception of a substance, whether we describe a cause in popular language as a thing or substance affecting some other thing or substance and producing an effect in it, or in the stricter language of the logicians call the cause an event or process which precedes another event or process and without which the second event or process, the effect, does not exist. I say ‘does not exist’ in place of the common phrase ‘would not exist,’ for our only means of knowing what would or would not, or can or cannot, exist is to discover what does or does not exist. The popular notion of a cause as a thing is inadequate, for a thing can only be a cause in respect of the events in which it is concerned. On the other hand, the logical notion of causality as a connection of events is inadequate so long as an event is regarded as an isolated occurrence and not as a process which if the event is a cause is continued into the event which is its effect. With such static or statuesque isolation of its events the causal relation is a piece of philosophical mythology. But a substance is a system of motions and whether the cause is a substance or a motion is all one. A cause is the motion of a substance, or a substance in respect of its motion. Thus the cause of the breaking of the window-pane is the motion of the stone or the stone in motion. There need not be for the causal relation any other substance than the motion itself. A thing in motion is only a very complex substance in motion. We have no difficulty in conceiving the substance of light as causing a chemical effect, even without introducing the notion of an etherial substance in which that motion is conveyed. The real reason why it is preferable to describe a cause wholly in terms of motion is that a thing is causal of its effect only in respect of the motion which is concerned. Thus a heavy stone breaks the window-pane in virtue of its velocity and mass. A grain of sand propelled with the same velocity might not have the same effect. We introduce the stone in order to note the mass which is engaged. But a thing may contain many qualities which are unessential to the effect. Thus, for example, a blow with a bat on the head or a blow with equal force of impact from an iron billet will produce the same effect. It is the business of science to disengage in the action of substances what is the part essential to the effect. The rest admits of variation. The thing may be in this sense only the vehicle of the cause, in Bacon's phrase.. The real cause is the motions which are continued into the motion which is the effect.

Causality is thus the relation of continuity between one substance and another, whether those substances be things or merely motions which we are not in the habit of calling things (e.g. light). The causal relation is the obverse side of the existence of a substance. For the category of substance communicates with that of existence. Every substance occupies a space-time. Now existence is other than and continuous with other existence, or it is in relation to other existence. Hence a substance, having existence, is at once different from another substance and continuous with some other substance. But all continuity is continuity of space-time; it is not merely stationary continuity but a moving one. Causality is thus the spatio-temporal continuity of one substance with another; and the cause is the motion which precedes that into which, let us say, it passes or is transformed. For we can find no words to describe something so elementary as this primitive crude relation except we borrow from particular instances of it, such as are implied by ‘transformation’ or ‘passing into’ or other such language. Substances share in the relational element of existence and that character of them is their causality in respect of some other substance.

Causality and uniform motion.

One matter of importance should be noted before we proceed. A substance or motion or group of motions is causal only if it is continued into a different motion. Thus there is no causality in the continuance without change of the same motion. A body perseveres according to the first law of motion in its state of uniform motion in a straight line unless subjected to the action of an impressed force. But we cannot say that the earlier part of the motion is the cause of the later into which it is continued. For the later part of the unchanged motion is the original motion or substance. The bare continuance of a motion signifies no causal action from something else. Indeed the first law, if I may venture on the statement, does little more than say this. It declares that any motion is as such a uniform motion, and that its path should be a straight line hardly adds to our knowledge, for it is probably true that the very definition of a straight line is that it is the path of a uniform motion; the fact of uniform, that is unaccelerated and unaltered, motion being anterior to the notion of a straight line. It is only when motion suffers some change of acceleration or direction that it postulates a cause, and we then ask what motion it was preceding this result which was continued into the change. For the continuity of a cause with its effect means not that the cause is as it were lost in the substance which it affects, but that it is added to the motions already existing there. Hence the very different effect produced by one and the same cause in different substances. The stone which breaks a window-pane may only bury itself in a soft window-cushion or a mound of earth.

Thus the continuance of a motion requires no cause but that motion of which the uniform motion is the effect and this is different from it. A motion does not cause its own continuance, is not as it were the cause of itself, but is itself. Self-causality, so far as that notion is legitimate, requires a different interpretation.

The purpose of this observation is to guard against a mistaken doctrine that the cause of an event is the immediately preceding state of the thing in which the event occurs. For this would allow the position of a body in uniform motion to be due to its preceding position. Causality would become an insignificant notion if it could be applied with this looseness. There is an additional objection to the doctrine. It implies that a causal process can be treated as a succession of states, the proviso being that they shall be in immediate sequence. But there is no such thing as immediate sequence in a continuous series, the very nature of which that there is no next term to any term. A cause is not an event followed by another event, as if the events were states of a substance. For out of such events neither continuity nor substance could be constructed. A state which is the cause of another state of the same thing can only be an ideal section of a process or motion. And thus interpreted, the proposition that any state of a thing is the effect of a preceding state can only mean, if it is to be true to Space-Time, that motions at any instant are continued into different motions by what is called immanent causality.

Transeunt and immanent causality.

All causality being the continuous passage of one motion or set of motions into a different one is transeunt. Immanent causality is nothing but transeunt causality between the substances which are contained within a substance. Thus, for instance, the passage of the thought of an action within our minds into the realisation of that thought in actual fact is (in part) immanent causality. A better example would be the internal repression of a wish where the whole action seems to go on within the mind, though undoubtedly it requires the presence of the body. The intramolecular actions of a body, or the interactions between the parts of an organic system, or the interconnection of movements within the system of an atom are other cases of immanent causality. The distinction is clearly a relative one, and merely a matter of convenience in description. A case of transeunt causality between two independent substances like the cricket-ball and the bat is immanent causality, if the ball and the bat and the intervening space are taken to be a single substance, as they may with perfect legitimacy be taken to be.

Moreover, the distinction is relative in another and more important sense. No substance is self-contained as being disconnected from the rest of Space-Time, and therefore from other substances. The immanent causality of an organism is sustained by the environment. Nervous action is affected immanently by nutrition, but nutrition is an effect of external substances, and nervous action contains essentially motor-response to the surroundings. When a thought brings about its own realisation in an act of will the immanent process is the transition of the thought into a perception and that is purely mental, but it implies the action of the body on its surroundings so as to produce the physical conditions, e.g. the lifted weight, which are perceived in the act of perception. To suppose an absolutely self-contained substance is in fact to omit the fact that it belongs to Space-Time, or rather perhaps it is to suppose that the Space in which it exists is stagnant instead of being essentially temporal. Even an atom is but a substance precipitated within the matrix in which all substance grows. The only self-contained reality in which all causality is immanent is the universe itself, and its immanent causality is but the transeunt causality of the existents it contains. But the infinite whole itself is not a cause, for the categories are only determinations of finites or other beings within Space-Time which these parts of the whole owe to the properties of any space-time. Thus when the universe is spoken of as self-causing, this is either an illegitimate phrase, used metaphorically of the whole; or, when it is used with a clear apprehension of its meaning, it signifies only that the various movements within the world are the outcome of other movements in a different distribution. In other words, the immanent causality of the universe is, to repeat ourselves, only another way of expressing that every existent in the world is in causal relation with other existents. Only in this sense is the world causa sui. All other self-causality is relative, it merely omits the dependence of the substance on the rest of Space-Time.

Summary.

Causation is thus a perfectly definite character of things; it is the continuity of existents within continuous Space-Time as subsisting between substances, which are themselves motions or groups of motions. Like all the categories it is pervasive and no substance escapes it. Causality is nothing less than this fundamental relation between substances. But it is also nothing more. No conception has been so persistently riddled with criticism. It has been declared from the point of view of logic to be either useless or superficial; from that of metaphysics to be self-contradictory. All these complaints seem to me to depend on taking it either to be more than it is and to have a meaning other than that which it has in the usage of science and especially of physics; or else to take it for less than it is, and to omit its characteristic features. To consider these criticisms in detail would be a task of much time, and all that I can hope to do is to touch upon them and in the main to let the exposition speak for itself. But before doing so it will be better to complete the positive exposition of causality, though there will necessarily be a latent reference to destructive criticism.

Cause and effect different.

In the first place, then, the cause is a different motion or set of motions from the effect. The mere continuance of the same uniform motion is as we have seen not a causal connection. The only identity between cause and effect is to be found in their continuity. We are not even to suppose that the moment at which the cause takes effect or the effect begins to be caused is as it were a meeting-point of the two motions; as if there were some single point in which the two processes overlapped. The continuity of the causal relation would be destroyed by the supposition. It would be a revival in a new form of the ancient puzzles of motion and the paradox of Achilles: the causal motion and the effect motion being broken up into steps of a progression. If this were the case the cause would not produce its effect, nor the effect begin, the point in question being the limit which the cause would tend to but never reach.

It might be urged that the cause is actually carried over into the effect; as when, to take a very simple case, a shove on a moving body accelerates its motion. But this is no mere persistence of the original motion; that motion is replaced by the acceleration of another motion. When the stone shatters the window there is not even the semblance of its continuance. The cause is only continued in the resultant of itself and the original motion of the patient. Now a resultant is what it is and different from the components. Other cases of a qualitative sort may mislead similarly, like Hegel's example of the rain, which is the same water in the air and in the ground which it wets. Really, the effect is something quite dissimilar: the falling water is distributed differenly from the resting water. In the action of digitalis on the heart, not even such accidental simplicity is to be found. The effect need not be like the cause and rarely is. And it never is identical with the cause. That would be uniform motion and the universe would be a blank.

Cause prior to effect.

Causality is essentially a temporally continuous relation and the cause is prior to the effect. Movements, and substances generally, may be simultaneous with each other but the relation is not one of causality. It is either, first, that of reciprocity where action and reaction are simultaneous; but a reaction is not the effect of the action but is the answering causality of the patient on the agent. This covers the simultaneous existence of qualities in the one substance where the qualities affect each other mutually. Or, second, the simultaneity may be the persistence of the same effect owing to the persistence of the cause; so that the effect of one dose of the cause is simultaneous with the next dose of the cause. In this way things, as bearers or vehicles of cause, and effect are simultaneous but not the cause simultaneous with its effect, not the particular dose of the cause simultaneous with its own effect. Or we may have simultaneity of motions which arise from points inherently contemporaneous. Otherwise simultaneity of cause and effect does not exist and would imply that the relation was merely a spatial one.

As it has been urged that cause and effect are identical with one another, so likewise it has been urged that cause, as it takes effect, occurs at the same instant with the effect as that effect begins. But this is either a tautology, or is untrue. The cause is the process in so far as it precedes the effect and the desire to find an identity of time between the two arises again, it is probable, from supposing the moments of the process to be contiguous instead of continuous.

It is essential therefore to causality that causation proceeds from before to after. Consequently it is only in a logical sense that the effect can be held to determine the cause as much as the cause the effect. We can only mean by this that when the cause and the effect are precisely stated they are reciprocal: when the cause, that is, is purged of what may indeed occur in a particular case but is accidental to it, and when the effect is stated in terms so precise as to presuppose one cause only and not a choice of several; when, to take the familiar example, the death from drowning is distinguished from the death by hanging, and the two not lumped together under the general designation of death. The reciprocity of cause and effect means then that unless there were the precise effect there would not be the precise cause. But such determination is logical and not real determination, and the effect cannot be interchanged with cause except as a basis of inference. We cannot in any real sense therefore say that the future determines the present, for the future is not yet and a future event introduces the order of Time. In that order the future does not determine but is determined. The present would not be what it is unless it causes the future which it actually does cause, but to regard it as dependent, except in the above logical sense, on the future is to take Time half as an accidental feature of the universe and to contemplate the world as spatial instead of spatio-temporal. Thus it is in no sense true that the future drags the present into its future condition as if it operated a fronte. All causality is a tergo.

This might seem to contradict what was said in an earlier chapter8 of the experience of the future in enjoyment. We anticipate something in our minds and this anticipation was described as the enjoyment of the future, not as present but as future. Now such anticipation leads on to performance, and hence it would seem that in this case at any rate the future is causal. Why not therefore extend this consideration and explain teleological action as action which is determined by the future end to be attained; so that animals and men are dragged to their issues from the future? The answer to this is to distinguish between the future event as it will be when it is actual, in which case it becomes not future but present; and the future as it is enjoyed, before it is realised. Such enjoyment is the future in idea, and this is the only way in which the future as future can be enjoyed. This future enjoyment is causal to its own realisation as a present. But this enjoyment drives us not a fronte but a tergo like all other causality. The transition is still from the before to the after. For the future as future precedes the future as it is when it has become a present and precedes it in the order of my enjoyment. In the same way my enjoyment of the past as past precedes in my enjoyment, as it should, the real present, for it is only by dragging the past up from the depths of memory, “the dark backward of time,” that I enjoy it as past. When, on the other hand, the future is said in any other than a purely logical sense to determine the present (just as much as the past obviously does), the future is taken to mean the actual distant event, and then the statement is untrue and falsifies the significance of Time. If Time be taken seriously all causality proceeds from actual present to actual future, and is never determined by the actual future. It may be determined by the future as future but this forms no exception to the proposition.

Finally, the causal relation is a relation of existents. One substance is the agent and the other its patient which suffers its effect. Agent and patient together form a relatively closed system and, as we have seen, within that system the causality is immanent. There is no causal relation between the infinite whole and any one of its parts. There is only such relation between one part and another. The whole system of things does not descend into the arena and contend with one of its creatures. The business of science in its search for causes (and it is not asserted that this constitutes the whole business of science) is to discover what precise events are connected as causes with what other precise events as effects. The task may be one of infinite difficulty and may at best lead only to probable propositions. The rules of the logic of discovery are rules of procedure in this quest. Where the causal connection can be established, it is done by an elaborate machinery of negative instances, by which the cause is narrowed down so as to contain only so much as is relevant to the effect.9 Where experiment is not possible other devices of approximation have to be used which supply the place of experiment. In the amusing prelude of the Sophist, Plato attempting to get a definition of the sophist employs his method of division in order to “hunt the sophist down to his lair.” What science does is to hunt down the cause of an effect to its lair. It may not establish exact connection but only a remote one. Yet it seeks, in the phrase of Mr. Venn, to screw the causal circumstances up closer and closer to the effect. This procedure is not open to the objection that the only satisfactory statement of a cause is the whole universe. If this were true the idea of cause would indeed retain a certain usefulness in practice, but as a theoretical basis of procedure in science it would be useless. But the objection rests on a misconception. It assumes that the operation of the stars is a motion which interferes with the causal act by which a man knocks another down; and does so because there is direct or indirect connection between all parts of the universe, throughout Space-Time. The question rather is whether the intimate causal relation mentioned is interfered with by the rest of the universe which undoubtedly sustains it. The question is the same as when we ask whether the properties of a triangle which undoubtedly imply the Space from which the triangle is delimited are affected by the sustaining and surrounding space. What science has to do is just to discover these limited, intimate, relations of existents which are called causal ones. Everything which it finds by inquiry relevant has to be included and becomes part of the substances involved. Everything which, though its presence is assumed, does not interfere so as to control or vitiate, lapses for the special causal relation into the position of an immaterial condition. So much at least follows from the fact that the world itself is not a category and cannot be a cause.

Causality no power, nor force.

We can now ask how far the modest but pervasive category of causality is open to the objections raised against it, which have grown into a formidable revolt against its authority. Hume's great service to this topic was that he purified the notion of causality of anthropomorphism; he denied or rather he failed to find in experience any power in the cause to produce the effect or any necessity in their conjunction. It is true he read experience amiss. For though no cause exhibits mysterious power, it possesses a relation of connection which Hume with his inherited conception of an atomic experience made up of single and isolated pieces was unable to detect. Subsequent philosophy has been engaged in restoring the connection which he overlooked. But the spectre of power and necessity which Hume laid has been busy with men's minds and is accountable for the discredit upon which causality has fallen.

No notion of power or necessity is contained in the conception of causality as a category. Still less is the connection an anthropomorphic one. The experience we have in our own persons of causality is so far from giving us a notion of mysterious and unexplained efficacy or power, that it is but an example of the same relation as we find outside ourselves in external events. Rather we must say that power is the continuous connection which we observe in ourselves and can more easily and directly observe in ourselves in enjoyment than outside us in contemplated events. Our power is an instance of causality; causality is not the work of power. But since the idea of a power in the cause to produce its effect suggests that the relation is presided over by something akin to spirit,10 some entity behind the relation which brings it into existence, we are perhaps well rid of the conception which is harmless if it were once “defecated” in Coleridge's famous phrase, “to a pure transparency.” Defecated conceptions still retain their body and colour in the general mind.

We need therefore shed no tear over power; and we may view with equal equanimity the discredit of force which has followed power or is in course of following it to the place where those notions are preserved, which are not so much false in themselves as such that the mind cannot safely be trusted to use. With power in the cause to produce the effect may go necessity of connection. The only necessity which philosophy can recognise is that of inference. But there is no necessity in things except fact. Nothing is added to causal relation by the adjective necessary. Every fact carries with it necessity, the necessity at least for the human mind of accepting it. There is no other necessity even in mathematics, which is often regarded as the special domain of that goddess. It is a fact that a triangle's angles are equal to two right angles, a fact which is discovered by inspection as all facts are discovered. It is only the extreme simplicity of the triangle, that it has none but empirical spatio-temporal character, which induces us to think that the connection of its form with the property named is necessary. For mathematics is no exception to the rule that science is empirical, and that its discoveries are won by attention to the nature of its subject-matter. Not even metaphysics is exempt, though its experienced material is non-empirical in nature. ‘Must,’ if I may repeat myself, was made for human beings in the relation of superior to subject. It has no part in science; though the science of man takes account of ‘must.’

Objections to causality: (1) from logical atomism.

Stripped of these dangerous anthropomorphisms the principle or, law of causality that any event has a cause means nothing more nor less than the proposition that a motion is continuous with some precedent motion. Such a principle is not necessary but is non-empirical as following from the nature of Space-Time and not from the nature of the particular events that happen to be connected in space and time. It is difficult to understand how in this sense it can be dispensed with, unless science is to avow itself a mere tabulation of isolated facts reduced to generalisations. It is worth while glancing at some of the reasons which seem to make the idea of cause dispensable. One of them is that causes and effects regarded as substances or things are in the first instance qualitative, and it is only in the initial stages of science that we are concerned with such relations of qualities. Fire expands bodies, digitalis stops the heart; propositions like these are merely the first steps beyond empirical descriptions. The further science goes the more it concerns itself not with connections of qualities but with measurement and with processes or motions; how much heat is related to how much elongation, what processes there are set up by digitalis which are connected with the heart's cessation. Moreover, it is not only relations between independent substances which demand investigation but in an eminent degree the constitution of things in terms of primary qualities; not what heat does but what heat is; what are the primary processes which underlie the world of qualities, or, in the technical phrase, which are the ground of qualities.

Thus the higher stages of science become to a large extent attempts to formulate in quantitative terms the processes which occur in nature. What we seek is not causes but formulae, expressible in equations. What place is here for cause? What is there in the law of gravitation which involves cause? Did not Newton himself in declining to make hypotheses as to the cause of attraction limit himself to the formulation of the facts compendiously stated in that law? What else is science but such a set of compendious formulae? “In the motions of mutually gravitating bodies,” says Mr. Russell,11 “there is nothing that can be called a cause and nothing that can be called an effect; there is merely a formula.” But apart from the fact that the deeper reasons for such formulae remain a subject of inquiry (the cause of gravitation is an actual problem of physics), a formula such as that of gravitation involves two elements. One is that of quantitative description of the motions that take place. On its other side, the formula asserts the reciprocal determination of two motions by one another, and this implies causality on the reasonable conception of what is meant by the causal relation. Qualitative causal laws are replaced by quantitative formulae, but so far as science aims at connecting together motions it is observing the law of causality, only in a less undeveloped form. I am bound to pass by the more explicit doctrine of Mach and his followers, that cause is but a useful means for shortening the work of description, for this doctrine implies a conception of thought which is inconsistent with our hypothesis of the relation of mind to things. Concepts are for us either realities or they are nothing. They may indeed be erroneous, but even then they are objective. That science is made by inventing concepts which are verified by experience is a perfectly true account of how we come to know. That our concepts are nothing more, are not (if we could but get the right ones) actual constituents of the objective world and not merely inventions of ours, this is at least not the principle on which we are conducting our inquiry.

Another reason for the discredit of causation is the sheer misconception of it for which philosophers are themselves in part responsible, that it means not a relation of connection but a frequency of conjoint occurrence. Two events apparently presumed to be disconnected may be taken to be cause and effect when if one is repeated the other is repeated—‘the same cause, the same effect.’ Attention has been diverted from the nature of causality itself to the nature of the conditions under which we can succeed in discovering causal laws; and the notion of the causality of a cause has been confused with the universality of the connection. An easy triumph is thus prepared for those suspect causes. There is no event which is repeated, and a conception of causality which is nothing but the repetition of a brace of events would indeed be useless. Now we have seen already that repetition, not bare identical repetition but under variations, is essential to the existence of a law, but is distinguishable from the contents of the law. The causal relation of two events is the relation between the events whereby they become immanent action in a single substance composed of the two events and of what is needed to unite them. The causal relation is not the repetition of the pair of similar events. The truth is that without the repetition we should not discover laws, and that at best owing to the great complexity of things and the great distance of actual repetition from mere repetition we can only hope for approximations to certainty. The practice of the logicians has been enough to show that the causal relation is not equivalent to the criterion ‘same cause same effect.” For it is vital to the discovery of causal relations that in the absence of a cause the effect is absent. This criterion it is which gives meaning to the negative instance. It is no doubt a legacy from Hume that the world should be broken up into disconnected events which are found together or in succession in experience. But Hume, to do him justice, did not attribute any causal relation to the events themselves, as his successors did, but to the expecting mind. I can only account for causality's still being held by those who profess adherence to Hume to be a relation, by supposing that relation is understood to be something that can be said about things and not a concrete set of transactions into which they enter.

The extreme of atomism is reached when causality, supposed to be equivalent to necessity and based on identical repetition, is considered to be an ideal limit constructed by the mind which is at the opposite extreme to complete independence of two things on one another. What science then has to discover is not causal connections, which are mental, but real correlations. No one would undervalue the formulae of correlation proposed with this end in view. But it is surely plain that this view is inspired by the fear of the bogey of necessity, and that unless we are to regard the world as made up of discontinuous units, against the spirit of our hypothesis, there is no meaning in correlation except as a first approximation towards the more intimate relation of direct or indirect causality; that we proceed statistically by establishing correlations where direct experimentation on causes is not open to us. The quest for correlation implies that events are determined, and determined in reality and not merely logically, by one another in a certain order.12 To discover such determination, the weighing of numbers may at one stage of a science be our only means. We aim at the plan of things by numbers where the plan is not immediately or directly accessible.

(2) from logical idealism.

It is from an entirely different point of view, in fact on the very ground of the systematic interconnection of things, that a different school of thought depreciates the relation of cause and effect in comparison with that of ground and consequent. We have followed them in maintaining that what matters in science is the connections of things. For us therefore the discovery of the cause of an event or motion or thing with qualities is the detection of what precise motion or group of motions or things or events is continuously connected with the effect. The cause and effect make a system involving process. But it is urged by the writers in question that a cause as a mere event in time contains something irrelevant to the characters of the system. Time has for them the taint of relative unreality and it infects the cause. And they point to systems like those in geometry where no Time, as they allege, is involved. Cause as an event in time is an incomplete ground, and the scientific ideal would be rather that of a system or the pattern of geometrical ones.13

It was this ideal which Spinoza employed, and the inadequacy of his effort to make causal connection satisfactory might have served as a warning. In truth it would rather seem that whereas, according to these writers, the relation of ground and consequent is fundamental and that cause and effect adds something irrelevant, the relation of ground and consequent eviscerates the causal relation of its essential element of Time: implication is a notion posterior to causation. Time is indeed supposed to be mere ‘time,’ mere succession, and it is such ‘time’ which is suspect. But there is only one sort of Time and a sensible event in time possesses that time-reality. If we mean mere time, a cause is not an event in mere time. If we mean real Time, Time is itself part of the ground. The ground of any consequent is fundamentally process and is spatio-temporal. Either therefore process is essential to the ground or else the cause or event in time which is irrelevant to the ground or which is the ground in an imperfect form is not the real event which is intended by cause. The preference of ground and consequent to that of cause and effect is in fact an attempt to translate what is essentially temporal, where Time is taken as real, into something stationary. To do so we must reintroduce process into the stationary contents of the ground, as when our subject-matter is itself historical, e.g. in psychology or physics. The example of a geometrical system is misleading. For stationary Space is but Space-Time with the Time omitted, and the omission is legitimate if it is only supposed to be provisional. The preference in question depends on the confusion of what is timeless with what is independent of any particular time, as all universals are.

Real grounds are to be distinguished from logical grounds, though they may coincide. The real ground of any event or character, when it is not merely the so-called formal cause, which is equivalent to the fact explained, as when vibrations of the ether are called the cause of light, being in fact identical with it, is a complex of motions of which the event or fact to be explained is the causal outcome. But logic, if we may anticipate a later chapter,14 is the science of truth, or of how our beliefs, as expressed in propositions, are to be systematised into a coherent whole at the guidance of reality. For it therefore the reason why or ‘because’ is not always the cause; whereas in reality the reason is the “moving why” of which Burns speaks. When A is equal to B, and C also, neither B nor the equality of A and C to B is the cause of the equality of A to C. All manner of good reasons for a conclusion are different from the cause of the fact stated in the conclusion. The cause is always a reason, but a reason need not be the cause. But we are not therefore free to regard the logical ground because it is the more general in logic as superior to the relation of cause and effect in the reality. Truth is like a work of art and has its own prescriptions, always dictated by reality. We go about to arrive at reality by methods proper to truth, and we are able to dispense in certain cases with direct reference to causal interrelation. But the ideals of logic cannot be used to depreciate the causal relation.

(3) from metaphysics.

These are difficulties which affect the use of causation in science and logic. Metaphysically it has been maintained that causation is not reality but appearance. For us since the universe of Space-Time divides itself into motions and yet retains its continuity, the continuous connection of motion with motion is as much ultimately real as the Space-Time of which it is the history. But the charges brought against it on metaphysical grounds may be lightly touched on here, for either they imply that causality is a relation which does not relate or they depend on misinterpretation of continuity. Thus when causation appears to be obnoxious to the infinite regress, for that A should cause B there must be some third thing C which moves A to its work, it is assumed that a cause is not itself causative. It is waiting for an inducement. Something, as Mr. Broad so well puts the point, is wanted to stir it into activity. But its real activity consists in passing over into its effect.

In the next place it is urged, by Mr. Bradley, that causation can neither be discontinuous nor continuous, or that it must be both, and is therefore contradictory. It cannot be discontinuous and must be continuous, for if it were discontinuous the cause would persist unchanged for a time and then suddenly change. Again, it is apparently assumed that for a cause to work it must have an inducement. But the cause does its work not by a change in itself but in leading on into something else. A cause might well remain unaltered for a time and then finding its patient produce its effect. The proposition that causation is not discontinuous is indeed true but not for the reason stated. Equally it is said causation cannot be continuous for the cause would then be without duration. “The cause must be a real event, and yet there is no fragment of time in which it is real.”15 This appears to mean that a cause must occupy a finite time in order to act; which is the assumption already rejected; and it appears also to assume that a continuum is put together out of adjacent points (in the likeness of spatial points), whereas the essence of a continuum is that being neither space-positions only nor time-positions only, all its points are instants and all its instants points. A continuum is a process and causation is a process. If the cause is something stationary, causation is indeed inexplicable. But it is in fact not stationary, and its continuity does not mean that at any one instant the cause is succeeded by something else which begins at the next instant but that any instant is the point of passage of a motion. To repeat an often-stated proposition, continuity is the conceptual formulation of motion itself, and, hard as it may be to say where cause ends and effect begins, yet if cause is itself a process and effect another and different one, the relation between the two is the transition of the one which is earlier into the later motion, or group of motions.

C. Reciprocity

The category.

Causality is a relation between substances in virtue of which a motion or group of motions in the one is continued into a motion or group of motions in the second and thus alters the pre-existing motion of the second substance. Now the second substance, or the patient, is already a motion or group of motions, and the effect which the cause produces is determined by the second substance as well. The transaction into which the two substances enter, so far as they constitute a closed system, is a two-sided and not a one-sided transaction. It is one in which each partner is cause and effect in turn. The situation which is the relation of the two substances is from the point of view of the first an effect on the second, but from the point of view of the second an effect on the first. The action of A on B is ipso facto an action of B upon A. In the transaction each partner exercises its own causality; the effect on B is a continuation of motions in A, and the effect in A is a continuation of motions in B. There is thus only one total situation arising from the relation of the two and it appears as an effect in B of A and an effect in A of B. Thus the pull of the horse, in Newton's example, on the rope attached to a heavy stone is a pull of the rope on the horse; the push which I give the earth by the intramolecular movement which follows my will to jump is the push of the earth upon me which actually is the jump that I am said to make. When a ball strikes another moving in the opposite direction, the motion imparted to the second in one direction is precisely the same transaction as consists in the rebound of the first ball. When a moving ball overtakes another moving ball the acceleration imparted to the one is a deceleration of the other, and the one ball loses its motion to the other, which it accelerates, just because of the internal movements of the second. One motion evokes an alteration in another motion into which it is thus continued, but it does not act upon the void, and the pre-existing motion which it accelerates is continued as an element in the same transaction into the acceleration in a contrary direction of the overtaking ball. In other and more familiar words, an effect is produced only in what resists. Every action is at the same time a reaction. But this does not do away with causality. The action of A on B is the causality of A. The effect on B is posterior to the motions in A. The reaction of B is its causality exercised upon A, and is posterior to the previous motions of B. Reciprocity between A and B is therefore reciprocal causality. Moreover, the reaction begins at the same moment as the action and two bodies in reciprocal action are simultaneous so far as concerns this moment. Thus the reciprocal attraction of the earth and the falling stone is a single transaction which is the beginning of the two opposite movements of the earth to the stone and the stone to the earth. It is this kind of case where the transaction is so obviously a single event, viz. the diminution of the distance of earth and stone, which has induced some to omit the element of causality, the earth on the one side and the stone on the other, and attend only to the mutual accelerations, inversely proportional to the masses of the parties engaged.

Corollaries

The simultaneity of two interrelated substances in respect of their action on each other is irrespective of the continued existence of the substances, such as we find in what Mill calls permanent causes, like the earth or other heavenly bodies. The substances might act on each other in virtue of their life and the life expire in the interaction. It would still remain true that the action and reaction would begin simultaneously in the dead substances left. Where we have permanent causes the two sides of the transaction are being constantly renewed and the two interacting processes persist beside each other.

Two interacting substances form a system or single substance. What is true of them is true also therefore of the substances within a substance, such as the qualities of a single substance or the parts of an organic whole. There is simultaneity between such actions and reactions within the substance, and here we have such account as I am able to give of the structural character of things apart from its intrinsic simultaneousness. The various parts of a substance sustain each other by reciprocity and so far there is simultaneity. But it is the result of causal process and therefore of succession.16

The same thing holds true of independent substances. When they come into relation they are in reciprocal action and simultaneous in respect of certain processes. This simultaneity is thus an outcome of the successive character of Space-Time. Once more both in respect of single things and in respect of the world as a whole, we come back to the truth that apart from the intrinsic necessity of some simultaneity of points, the fact that at any one moment Space is filled with some event or other is derivative from the successiveness of Space. A purely simultaneous Space would be a Space which perished with its perishing moment. A Space which is occupied by Time at various stages in the intrinsic succession of Time allows both for the persistence of Space and for its complete occupation at any moment.

Mechanical and organic reaction.

Action and reaction are conceptions drawn from mechanics and founded as now we see in the nature of Space-Time itself. The question may be raised whether organic reaction falls under the same head. In particular it might be asked, if a luminous body is the cause of our visual sensations, do we in vision react on the luminous object? It causes vision in us, but do we alter it? The answer will illustrate the real nature of action and reaction. For the character of the reaction depends on the nature of the body affected, and so does the effect produced by the cause. Now owing to the complexity of an organic body the characteristic effect of the cause may be only a remote effect. Thus the immediate mechanical effect of light is pressure on the eye, and there is mechanical reaction to this. But the psychological effect is remote and arrived at through a long chain of action, whether chemical or not I need not inquire. It takes time for the mental effect of light to be produced, but when it is produced there is at the same time an action on the part of the organism of motion which is commonly spoken of as the motor reaction. This motor reaction is an integral part of the whole situation in which the action of the light ultimately takes effect. For it is a short-sighted insight which supposes that the sensation of light is something which occurs first and then releases the motor action which ultimately leads to turning the eyes to the source of light. We may rather see reason to believe with Mr. C. S. Myers17 that the actual sensation depends on the type of the motor response and that the sensation emerges with the motor process. Thus when the light produces its effect on the centres of vision the organism with its preformed structure is reacting towards the external world.

We must thus note first that the reaction of the organism may be remote as compared with the first effect of the stimulus. And again it will be very complex in the end if the whole substance directly or indirectly affected is complex. Hence, to quote a famous argument to which we shall recur later in another connection, a telegram may leave me cold which owing to its contents may throw another person into profound agitation of mind and of response. In the next place the essential character of the reaction may be masked by the difference of the conditions here and in a simple mechanical response. For the reaction may take effect not so much on the source of stimulation as on other objects. In general and as a matter of fact organic reactions are in their outcome directed towards the stimulus. The organism performs motions which are designed to secure more of a pleasant and less of an unpleasant stimulus, by what Mr. Baldwin has called a circular process, or a process of imitation, which repeats itself. The sight of a tasty thing reacts in the seizing of it to eat. Our reactions are in the first instance practical and do tend to return upon the object. But the object being only remotely the cause of the visual reaction, the reaction to it may be directed on some different object. Thus in purely intellectual apprehension of the fruit the reaction may take the form, in the end, of speech. Or an insult may be avenged not on the person of the culprit but on some one else, or a man may recoup himself in the circle of his home for the vexations he has suffered from his business. These are complexities arising from the complexity of the situation and of the organism. What concerns us to observe is that any action on the organism issues upon the external world sooner or later in some part of it, whether directly connected with the original source of the stimulation or not. The organic reaction considered in its complexity is the issue of the organism's affections in effects upon the external world. And they are not without grounds who look upon an organism as an apparatus whereby actions received from outside are converted into effects upon the outside world again. The simplicity of mechanical action and reaction is not to be expected in these cases where we compare the ultimate source of action and the ultimate shape and locality of reaction. The equivalence of action and reaction may however be traced at every stage of these highly complex transactions.

• 1.

  For the subjects of this chapter, especially Substance, I have found much profit in Mr. C. D. Broad's Perception, Physics, and Reality (Cambridge, 1914), ch. ii. ‘On Causation.’ For substance, see especially pp. 94–6, which confirmed and helped me in views which were already in formation in my own mind. I have borrowed some of his language and illustrations.

• 2.

  On the use of the word relation as between the space and time elements themselves, see some further remarks later, ch. ii. p. 324.

• 3.

  See on this subject later, ch. ix. p. 325.

• 4.

  For the problems raised by the lapse of intervals of mental life from our consciousness see later, Bk. III. chs. i. A and vi.

• 5.

  Book III. chs. vii., viii.

• 6.
  The above applies, at any rate directly, only to qualities (a) of different modality, (b) on die same level; e.g. the different secondary qualities of matter, of which I am mainly thinking. As to (a), the molecules of a tuning-fork vibrate with a single vibration compounded of those of the fundamental tone and the overtones. Is there here a single quality, or several separate qualities heard confusedly? (b) A higher quality, life, is a movement (see Book III. ch. ii. B) of living substance which carries with it movements, say of colour, in the material parts. I do not discuss these difficulties.

  For the question under (a), see F. Brentano's Untersuchungen zur Sinnespsychologie (Leipzig, 1907), an extraordinarily stimulating book, to which I shall have to refer hereafter (Bk. III. ch. v., on the intensity of sensations). He speaks, however, of psychological sensory contents and the space of sensation (Empfindungsraum), not as I do of external qualities in an external Space.

• 7.

  I have been helped in this chapter by Mr. Broad's discussion of causality (Perception, etc., ch. ii.).

• 8.

  Book I. ch. iv.

• 9.

  Bosanquet's Logic, vol. ii. ch. iv. pp. 115 ff. (eds. 1 and 2).

• 10.

  In the sequel (Bk. III. ch. ii. B) it will be maintained that ultimately there is in all things something which corresponds to spirit in ourselves. But the point of that doctrine is not so much that things are spirits, as that spirit is only an advanced form of something which is found lower down in all things. Our awareness of power is but our consciousness of the causal relation between our will and our acts. The mischief of the ' conception that a cause has power to. produce its effect is that it introduces some mysterious element of connection other than that of simple continuity. Hume went too far in the opposite direction. For us causality is not so much an example of power as power is an example of causality.

• 11.

  ‘On the notion of Cause,’ Proc. Arist. Soc. N. S. vol. xiii., 1912–1913, p. 14. Reprinted in Mysticism and Logic (p. 194).

• 12.

  Compare chapter v. on ‘Contingency and Correlation—the insufficiency of Causation’ in Mr. Karl Pearson's Grammar of Science, Part I. (London, 1911, ed. 3), with Mr. A. Wolf's remarks in Proc. Arist. Soc. vol. xiii. N. S., ‘The Philosophy of Probability,’ §§ 3–5.

• 13.

  For the topic of this section see Bosanquet, Logic, vol. i. pp. 264 ff. ed. I (252 ff. ed. 2).

• 14.

  Bk. III. ch. ix. B.

• 15.

  Appearance and Reality, ch. vi. p. 61 (ed. 1). C. Reciprocity

• 16.

  Above, ch. vi. A, p. 276.

• 17.

  British Journal of Psychology, vol. vi., 1912: ‘Are the intensity differences of sensation quantitative’ I. § I. See later, Bk. III. ch. v.