IN the Republic Plato puts the coping-stone upon his ideal theory by asserting not merely the existence of a number of independent ideas, but the systematic unity of all ideas under one supreme principle, a principle at once of all reality and of all thought. But, with this conception of the ultimate unity of all things with each other and with the mind, Plato's philosophy seems to enter upon a second stage of development, which carries him still farther away from the abstract idealism commonly attributed to him. For hitherto he has looked upon the idea mainly as a unifying principle—a principle which we need not, indeed, take as a mere abstraction, but which is so far abstract as it leaves out many of the aspects of the manifold and changing phenomena, and has no differences or determinations but such as flow from its own nature. There is, however, a great danger of misunderstanding when such almost exclusive emphasis is laid upon the unityof the idea, as if it had no distinction of elements within itself at all; and this misunderstanding might go still farther in view of what Plato says as to the idea of good being ‘beyond being’ and ‘beyond knowledge,’ if this were taken as excluding its immanence in both.

It is, therefore, noticeable that in the dialogues which follow the Republic Plato begins to change his point of view, and to speak of it as the business of philosophy, not only to rise from difference to unity, but also to trace the way downwards from unity to difference and multiplicity. Already in the Republic, where the dialectician is primarily characterised as one who ‘thinks things together,’ it is indicated that, after he has reached the highest idea, he must seek to develop all the other ideas from it. But in the Phaedrus the two processes of synthesis and analysis, συναγωγή and διαίρϵσις, are distinctly put on a level; and only he who is able rightly to perform them both is thought worthy of the name of a dialectician. He must be able, Plato declares, “to take a comprehensive view of the multitude of scattered particulars and to bring them under one form or idea, for the purpose of defining the nature of the special subject which he wishes to discover.” But he must also “be able to divide into species, carefully attending to the natural joints by which the parts are severed and connected, and not breaking any part, like a bad carver.” “Of these processes,” says the Platonic Socrates, “I have always been a lover, seeking by their means to make myself able to speak and to think. And if I can find anyone who is thus able to see up to the one and down to the many, I am ready to follow in his footsteps as if he were a God.”1

Plato illustrates this view by a criticism of the teaching of rhetoric by some of the leading orators of the day, as resting upon a number of empirical rules about the use of words, about figures of speech, or about the commonplaces of argument, and not based upon any comprehensive view of the nature and object of oratory, and of the different elements and conditions that go to the making of an effective speech. In discussing the nature of anything, we must, he declares, first enquire whether it is simple or multiform; and, if it is simple, we must ask what capacity it has of acting upon other things and being acted on by them; while, if it has more forms than one, we must determine how many they are, and what capacity of acting or being acted on belongs to each of them. Without such a preliminary analysis, our procedure will be like the groping of a blind man. Now, as rhetoric has to act oil the souls of men, we must begin in this case by asking what is the nature of the soul, and whether it is simple or multiform like the body. Then we must enquire how it, or any part of it, acts or is acted on, and by what agencies. And, lastly, we must classify the different kinds of argument, as well as the different kinds of soul and the affections of which they are susceptible; and we must fit the several arguments to the several mental constitutions, and show how such and such souls are necessarily wrought upon by such and such discourses. If we proceed on this method, our rhetorical art will be not a collection of unconnected empirical rules, but a real scientific system; and any speech we construct in accordance with its prescriptions will be not an aggregate of unconnected arguments and exhortations, but an organised whole. In Plato's own words: “This, I think, you will admit, that every speech ought to be composed like a living being, which has a complete body of its own, and is neither without head nor without feet; in other words, it ought to have a beginning, middle, and end, all in harmony with each other and with the whole.”2

This conception of the equal importance of distinction and relation, of analysis and synthesis, dominates all the later dialogues. Science is henceforth presented to us as an organised system of parts, which are clearly distinguished from each other, yet essentially bound together by the one idea or principle which is realised in them. In Plato's exposition of this view, however, we find something of the same ambiguity which lay in his first account of the ideal theory. And, as there it was sometimes doubtful whether the idea was to be regarded as merely the abstraction of some common element in the particulars, or as a principle which explained their differences; so here, it is not quite clear whether Plato is merely referring to the division of a genus into subordinate species according to some arbitrarily chosen principium divisionis, or whether he means that the higher idea is to be taken as itself supplying the principle of its own division, and the subordinate ideas as having a necessary interconnexion, such that each implies and is implied in all the others. As, therefore, in the former case, we had to ask whether the idea is an abstract or a concrete universal, a common element or a principle which explains a certain compass of differences; so in the latter case, we have to ask whether the relations of the parts that fall under the idea is that of co-ordinate species which do not stand in any essential relation to each other, or whether it is that of parts which cannot be conceived except as belonging to one whole. Is Plato, after all, only aiming at a mere classification of different existences from an arbitrarily chosen point of view, or is he seeking to comprehend the intelligible world, and every distinct part of it, as a system of members which are in organic unity with each other?

It is not easy to solve this problem; indeed, it cannot be solved by a simple ‘yes’ or ‘no’ For, in the first place, before we deal with it at all, we have to separate two questions which Plato does not always clearly distinguish—the question as to the κὁσμοςνοητὁς, the system of ideas when viewed in themselves, and the question as to the objects of the phenomenal world, which are said to participate in these ideas. In regard to the latter, it is abundantly evident that, according to Plato, particular phenomenal existences are subsumed under ideas without being completely determined by them. Indeed, it is the primary characteristic of the world of sense and opinion that the ‘many’ in it is not completely determined by the ‘one’; or, in other words, that its differences and its changes are not the pure manifestation of ideal principles, but in many ways fall short of them. Of this relation of the phenomenal to the ideal world, I shall have to speak in a later lecture; for the present we have to consider the pure relation of ideas as elements in the intelligible world.

But, even from this point of view, the intention of Plato is not without some ambiguity, especially when we consider the way in which he employs the method of division in the Sophist and the Politicus. For in these dialogues he seeks to define an object simply by taking a large genus in which it is included, and dividing it into two species by any principle of division that suggests itself; then, subsuming the object under one of the species, he proceeds again to divide that species by another arbitrary principium divisionis; and so on till lie reaches an infima species which cannot be further divided. We can, however, hardly suppose that Plato means us to take this method quite seriously: indeed, the six examples of division by which the Eleatic stranger reaches the definition of the Sophist seem rather intended to exhibit the defects of such an arbitrary process, and to illustrate the fallacy which Aristotle points out when lie says that division is a ‘weak inference.’ And we have to observe that in the latter part of the dialogue Plato directs all his efforts to illustrate a view of ideas and their relations, which is entirely opposed to this. Indeed, the aim of the whole remarkable group of dialogues which includes the Theaetetus, the Sophist and the Parmnenides, seems to be just this—to develop the doctrine that universals are not abstractions but concrete principles of unity in difference; and that they have a community with each other, which we can only express by saying that each contains or involves all the others.

This view of ideas seems to have arisen in Plato's mind in connexion with a careful study of the conflicting views of the earlier Greek philosophers which, till this period, had not received much attention from him.3The controversy between the two great schools, that of the Eleaties who insisted upon the unity and permanence of objects, and that of the Heracliteans who insisted exclusively upon their multiplicity and changefulness—suggested to Plato the idea that neither of them could be regarded as adequate, and that the truth must lie in some tertium quid, which should at once transcend and combine them both. Hence he declares in the Theaetetus that it is above all necessary for us to examine carefully the two opposite theories of those who set everything in flux and of those who would make all reality immovable. And then he adds that “if we find that neither of these schools has anything reasonable to say, we shall be absurd enough to think that we, poor creatures, are able to suggest something to the purpose, while we reject the views of ancient and famous men.”4 If, therefore, the ideal theory were to vindicate its claims, it must show itself able to unite the ‘one’ and the ‘many,’ and to prove that they are not absolutely opposed but rather require each other. Accordingly in these dia logues Plato seeks to prove, on the one hand, that the views of these two schools are one-sided and self-contradictory, and, on the other hand, that the ideal theory is able to take up into itself the elements of truth that are in both. And it is important to notice that he directs his criticism both against the objective aspect of these philosophies, as theories of being, and against their subjective aspect, as theories of knowing; and that from this point of view he identifies the Heraclitean philosophy with Sensationalism, and the Eleatic philosophy with an abstract Idealism which might find some support in his own earlier statement of the ideal theory.

Thus, in the Theaetetus Plato deals at once with the Protagorean doctrine that finds the measure of all things in the sensation of the individual, and with the doctrine of Heraclitus that all things are in flux; and he attempts to show that, both severally and together, they lead to the result that nothing exists or can be known. For if the Heraclitean view be true, and everything is in continual process, ever becoming other than itself, no determination either of quality or quantity can remain even for a moment, and nothing can be said even to be. If there be nothing permanent, there is no reality in anything. And this, again, implies that no knowledge is possible; for, ex hypothesi, there is nothing left to characterise the object as one thing rather than its opposite; and that which is always changing in every aspect of it, can not be known even as changing. Again, looking at the question from the side of the subject “pure Sensationalism is speechless”; for we can neither distinguish one sensation from, nor identify it with another, unless our thought goes beyond the sensation itself. “There is, therefore, no knowledge in the impressions of sense, but only in the discourse of reason in regard to them.”5

In the Sophist, again, the same results are shown to follow from the opposite doctrine, that is, from the abstract Eleatic assertion of the absolute unity and permanence of being; for, if no difference be admitted in the aspects of the One, we cannot say anything about it. Even to affirm that ‘the One is,’ implies some distinction between being and unity. Every predication, in short, if it means anything, involves a relative difference between the subject and the predicate, and bare identity means nothing at all. Similar reasons make it impossible to give any meaning to a permanence which is without change, movement or activity. Neither absolute motion without rest nor absolute rest without motion can be conceived, but only the union of the two—that which combines motion and rest, or which rests in one point of view and moves in another.6 But if in this way pare unity and permanence, and pure diversity and change be proved to be each of them unintelligible, if they can neither be nor be known, what is the necessary inference? It is obviously that the only thing that can either be, or be known, is the one-in-the-many, the permanent-in-change. The Eleatic and the Heraclitean theories equally failed, because they attempted to divorce two elements which are inseparably united.

This result Plato immediately applies to the ideal theory. By its aid he sets aside the ordinary conception of ideas as self-referent abstractions, which are without any difference in themselves and without any relation to each other—a conception which had derived some support from the language of Plato himself in his earlier dialogues. Even in the Republic, he had spoken as if any community or connexion between different ideas would be a source of confusion as to their real nature.7 But now he points out that, if ideas are to be conceived as principles of being and of knowledge, they cannot be taken as abstract identities without difference, or as unmoved types unrelated to each other and to the mind. As principia essendi, they must be unities of differences, and each of them must have a definite place in the system of the whole, differentiated from the others and yet related to them; and as principia cognoscendi, they must have community or relationship with the mind, and they must be conceived as forms of its activity as well as of the activity of the object.

In the Parmenides, this view is confirmed by an examination of the ideal theory with special reference to the problem of the one and the many. Plato begins the discussion by casting contempt on the easy dialectical tricks of the sophists and rhetoricians, who proved that the one is also many, only by pointing out that the same individual in spite of his identity has many parts or attributes. But the true question of the one and the many relates to the difference and unity of these ideas in themselves, and not as they may be accidentally combined in one subject. “If, then, any one should attempt to show that the one and the many are the same, taking for his illustration the case of stones or trees and the like, we shall say that he shows, indeed, that something is at once one and many, but not that the one itself is many, or the many one. Thus he does not tell us anything worthy of wonder, but only what anyone can see for himself. But if, as I have just said, he were first to divide such pairs of ideas and set each idea by itself—say, the ideas of similarity and dissimilarity, of the one and the many, of rest and motion—and should then show that these opposites are capable of being combined and separated, I should be greatly surprised.”8 Parmenides, however, proceeds to show that this result at which Socrates would wonder so much, can be actually realised: firstly, by a criticism of the theory of ideas, viewed as abstract universals; and secondly, by following out the hypotheses of the existence and of the non-existence of both of the one and of the many, in all the various senses in which these hypotheses can be taken.

In the first part of this investigation Plato shows the difficulties of the ideal theory, so long as ideas are taken as the common elements in various particulars, and yet at the same time as independent substances. For then, he asks, what can be meant by saying that many things participate in the same ideas? If the idea be an independent substance, like a sail drawn over many objects,9 it is impossible that it should be wholly in each of the things that participate in it: yet it would be absurd to suppose that it was divided among them; for, in that case, it would cease to be one idea, and would thus lose all its meaning. Again, if the idea corresponds merely to the common element in many particular subjects which in other respects are different from each other, it will not be essentially related to these subjects, and cannot explain their existence. It will only be accidentally present in them along with their other qualities; or if it be essentially bound up with them, it must be through some third idea.10 But, again, if that third idea be only a common element in the first idea and the particular subjects brought under it, it will only be accidentally related to both, and a fresh idea will be required to establish connexion between them; and so on ad infinitum. Nor will it alter the case if we suppose that the idea is an abstract type, and the subjects are merely like it; for if likeness requires an idea to explain it, we again fall back into the same processus in infinitum. It appears, then, that we can explain nothing particular by means of an abstract universal.

There is obviously no way out of these difficulties, so long as the idea is taken simply as a common element in a number of species and individuals, and not as a principle which manifests itself in their difference and binds them together into one systematic whole. Such an organic principle alone can be conceived as whole in all the parts brought under it, and, therefore, as needing no tertium quid to unite it with them. Now, looking to the way in which, both in the Theaetetus and the Sophist, Plato seeks to carry us beyond the abstract theories of the earlier schools, we cannot but suppose that his intent is to bring us to this conclusion, that is, to make us accept the doctrine that the true universal or idea is a concrete or organic principle, which is one with itself in all the diversity of its manifestations; though, as is often the case, his dialectic is negative rather than positive, and he leaves us to draw the inference for ourselves.

Still more important is the application of the same method to the relation between ideas and the mind. If ideas be taken as objective principles, complete in themselves apart from any relation to our thought, Plato argues that they can be nothing for us; and the objects of knowledge, though called by the same names as the ideas, will have no relation to them. They will be completely transcendent and removed from our consciousness: and, if there be any consciousness which grasps them, it will have no community or connexion with our minds. Yet, on the other hand, if we reject this hypothesis, and take ideas merely as our thoughts, which, as such, exist only in our minds, they will be reduced to subjective affections; and it will be impossible to explain how through them we can know anything objective. It is, however, absurd to regard thoughts in this way, as mere subjective states of an individual consciousness. “Why,” asks Parmenides, “must not a thought be a thought of something? And, if so, must it not be the thought of one definite object? And must not this object be an ideal form, which remains the same in all cases in which it is realised?”11 In other words, Plato points out that the conceptualist hypothesis here suggested will not help us out of any of the difficulties involved in objective idealism; and that, indeed, it involves an ignoratio elenchi. For ideas or universals cannot be taken as mere states of mind referring to nothing beyond themselves. But if not—if through universals we know anything—this implies that in some sense they are in the objects known through them, as well as in our minds; and, indeed, that they are just the principles that give definiteness and unity to these objects, and make then capable of being known.

But if we can neither say that ideas are real principles without relation to mind, nor yet reduce them to states of mind, if, in other words, we can neither treat them as purely objective nor as purely subjective, what follows? Obviously the only remaining alternative is that the distinction between thought and reality, subjective and objective, must be regarded as a relative difference—a distinction between factors in a unity, which imply each other and which cannot be separated. On this view reality cannot be conceived except as the object of thought, nor thought except as the consciousness of reality. On the one hand, to take reality as complete in itself apart from thought, or as only accidentally related to thought, is essentially to misconceive its nature; for every characteristic by which objects are determined as such, can be shown to involve their relation to a conscious subject; and the attempt to abstract from this relation would compel us to treat theirs as unknowable—as something external to the life of the subject, and which, therefore, the consciousness of the subject cannot reach. Indeed, it would be impossible on this hypothesis to explain how even the imagination of such objective reality should ever present itself to consciousness at all. On the other hand, it is equally irrational to take thoughts as mere states of the subject without reference to reality; for it is in such objective reference that all their meaning lies. Indeed, apart from such reference, we could not apprehend them even as states of the subject.

We must, then, regard an idea, in the Platonic sense, as a principle which transcends the distinction of subject and object, of thought and reality, and which manifests itself in both. We are not, indeed, required to deny that there is an accidental, or merely subjective aspect of knowledge—as realised in a finite individual and under the special conditions of an individual life; but we can never take the consciousness of an object as a mere state or quality of the individual subject, as determined by such conditions. We must regard such consciousness, however partial and inadequate it be, as the manifestation in an individual form of the one principle which is the source of all being and all thought. While, therefore, we uphold the relative distinction of thought and reality, we must be careful not to elevate it into an absolute difference; for this would leave us with, on the one side, an idea which is merely a state of the subject, and, on the other side, a reality which is unknowable. We must repel the Berkeleian tendency to dissolve objects into ‘mere ideas’; but at the same time we must remember that as objects they are relative to the subject; for reality as intelligible implies the intelligence, and the intelligence, on its part, is nothing except as conscious of reality. We cannot understand either the process of being or the process of thought, unless we realise that they are only different aspects or stages of the same process; and that, in their utmost divergence, they are held within the unity of one principle or, as Plato expresses it, of one idea.

But when wo adopt this view of ideas, we are led to a further result, which also is recognised by Plato. As we have seen, Plato requires us to conceive the idea as the unity of the opposite principles of the Eleatics and the Heracliteaus, and, therefore, as combining in itself unity and difference, permanence and change. This, however, means that an idea must be conceived as a self-determining or active principle; since only that which is self-determined can be said to transcend these oppositions, to maintain its unity in difference and its permanence in change. It alone can combine movement with rest, because its activity has its source and end in itself. But where are we to find such a self-determined principle? It is obviously a conception which can find its realisation, or at least its adequate realisation, only in a mind. Hence we do not wonder to find Plato declaring that “Being in the full sense of the word (τò παντϵλω̂ς ὄν) cannot be conceived without motion and life, without soul and mind.”12 In other words, ideas, merely as such, are deposed from the highest place as principles of thought and reality and the place is taken by souls or minds. Accordingly, in the Phaedrus, in a passage to which we shall have to return, the soul is spoken of as the one principle which is immortal and unchangeable, because it alone is self-moved or self-determined and, therefore, the cause of all determination or change in other things.13 And it is obviously impossible to admit such a conception of soul or mind without depriving ideas, as such, of the position which they have hitherto occupied.

But with this a new dilliculty arises: for, if “reality in the full sense of the word” be only found in souls or minds, what are we to make of other objects? Are we to say that they are unreal appearances? Then we shall have escaped the paradox of subjective idealism—that the only objects we know are our ideas as states of our subjectivity—only to fall into what we may call the paradox of objective idealism, that the only objects which we can recognise as such are minds. This difficulty does not escape Plato; and accordingly we find him arguing in the Parmenides that, if things participate in ideas, and ideas are thoughts, we are reduced to the dilemma, either that ‘all things think,’ that is, that all things are minds: or, that “they are thoughts which exist without being in any mind that thinks them.”14 But, if we reject the second alternative as absurd, we seem to be driven to the conclusion that nothing has real existence except minds and their states, and that all other existence is an illusory appearance. Can this conclusion be taken as in any sense reasonable? And, if so, what is Plato's attitude towards it?

Now, there is a sense in which every idealist must admit that the only object of mind is mind. Everyone who holds that the real is relative to mind, and, therefore, that the difference between mind and its object cannot be an absolute difference, must acknowledge that whatever is real, (and just so far as it is real,) has the nature of mind manifested in it. Reality cannot be alien to the subject that knows it, nor can the intelligence comprehend any object except as it finds itself in it. In other words, objects can be recognised as real, only if, and so far as, they have that unity in difference, that permanence in change, that intelligible individuality, which are the essential characteristics of mind.15 At least we can regard an object as an independent and substantial existence only in so far as it possesses such characteristics.

It is not, however, necessary to infer from this that every object, which is in any sense real, ‘thinks,’ or is a conscious subject; for we do not need to take reality as a simple predicate, which must be attached to everything in exactly the same sense. We may, and, indeed, we must admit that there are what Mr. Bradley calls differences of degree, or what might perhaps even be regarded as differences of kind, in reality. In its highest sense the term ‘real’ can be predicated only of a res completa, of that which is complete in itself, determined by itself, and, therefore, capable of being explained entirely from itself. But this does not involve the denial of reality even to the most transient of phenomena, if it be but as a phase of something more substantial than itself. There is a certain gradation in the being of things, according to the measure of their independence. From this point of view, every systematic whole must stand higher in the order of reality than an aggregate of unconnected, or externally connected parts; and a living being in its organic individuality would be regarded as more real than any inorganic thing. In the sphere of the organic, again, we may find many grades of being, from the simplest vegetable cell up to the highest and most complex of animals. But while all such beings are conceived as in a sense substantial, in so far as their existence is referred to a centre in themselves, it is only in man that we find that permanent self-identity, that unity with himself in all difference and change, which is needed fully to satisfy our conception of substantial reality. He only can be properly said to have a self, since he only is fully conscious of it. And it is only as self-conscious that he is able to refer all things to himself and so to generate a new world for himself; or, if we prefer to put it so, to reconstitute the common world of all from a fresh individual centre. Even here, however, we cannot stop; for no finite spirit is complete in itself. As finite, he is part of a greater whole, the member of a society which itself is but one phase of humanity, conditioned by all the other phases of it, and, indeed, by all the other elements that enter into the constitution of the universe. We can, therefore, find that which is absolutely real or substantial only in a creative mind, from whom all things and beings must be conceived as deriving whatever reality or substantiality they possess.

Now, if we adopt this point of view, it is possible to regard all objective reality as kindred with the intelligence, without going on to assert that nothing exists except minds and their states. In other words, it is possible to maintain that every intelligible object is a partial form or expression of the same principle which is fully expressed in the intelligence, without denying the relative reality either of the inorganic or the organic world, and without, on the other hand, treating every mind as an absolutely self-determined being.

We cannot, however, without much qualification, attribute any such conception to Plato. Plato, indeed, speaks of grades of being, but only in connexion with the theory of metempsychosis; that is, he speaks only of the grades of elevation or degradation through which the individual soul may pass. All organised beings, or rather we should say all animals—for nothing is said of plants—are conceived by Plato as having in them a principle of self-determination to which he gives the name of a soul; and all souls are treated as fundamentally identical in nature. But this nature is shown in its purity only in the Divine Being; or, if in men, only in those men in whom the intelligence reaches its highest development; and, pre-eminently, in the philosopher who has grasped the central idea of good, and, therefore, beholds all things sub specie aeternitatis. And while the soul thus can rise to the highest, it can also sink to the lowest, becoming more and more immersed in the body, till the life of intelligence is lost in the obscure animal motions of sensation and appetite. So far, therefore, all real or substantial objects are conceived by Plato as souls or minds, in a more or less elevated or degraded condition. The doctrine of metempsychosis, in fact, enables him to hold that, in the strict sense of the word, reality is confined to souls or minds, without thereby denying that it belongs to every being that has life, or at least animal life, in it. On the other hand, when we descend further in the scale of being, this mode of explanation fails him, and Plato, it would seem, must be driven either to regard all inorganic objects as mere appearances, or else to imagine that they are somehow living and organic. And the latter alternative he would be obliged to reject; for, as the body is conceived as obscuring and thwarting the life of the soul, it cannot be referred to the same principle with that life; and its existence, even as an appearance, becomes a difficult problem. We are therefore compelled to recognise that at this point Plato's idealism passes into dualism; and it becomes necessary for us to enquire into the exact form which his dualism finally took—a question which must be answered mainly from the Philebus and the Timaeus.

Before, however, we can deal with this subject, we have to consider more fully Plato's doctrine of the soul, and, particularly, his treatment of the question of immortality.

• 1. Phaedrus, 266 B.
• 2. Phaedrus, 264 C.
• 3. Aristotle (Metaph., I. 6) says that the development of the ideal theory was due to a combination of the Socratic view of universals with a conception of sensation and its objects due to the philosophy of Heraclitus. But we do not find this connexion of Sensationalism with the Heraclitean philosophy referred to except in the Theaetetus, and the earlier development of the ideal theory in the Meno, Gorgias, symposium, Phaedo, and Republic does not appear to be connected with any direct Heraclitean influence.
• 4. Theaetetus 181 B.
• 5. Theaet., 186 D. ἐν μέν ἄρα τοι̂ς παθήμασιν οὐκ ἔνι έπιστήμη, ἐν δέ τῳ̂ πϵρἰ ἐκϵίνων συλλογισμῳ̂. Of course, syllogism has not yet its technical sense.
• 6. Sophist, 249, 3.
• 7. Rep., 476 A.
• 8. Parmenides, 129 D. It might be suggested that by putting this into the mouth of Socrates, Plato was acknowledging that there was a time when it applied to himself.
• 9. Parm., 131 B.
• 10. Parm., 132 A. This is the τρίτος ἂνθρωπος argument, which is so often mentioned by Aristotle. though he takes no notice of the discussion of it in the Parmenides.
• 11. Parm., 132 C.
• 12. Sophist, 248 E.
• 13. Phaedrus, 245 C. It is to be noted that the dialogue in which Plato first speaks of the soul as self-moving and immortal is also the dialogue in which he first asserts that dialectic is a process both of analysis and synthesis, and that its object is to attain to a systematic view of things.
• 14. Parm., 132 C. νοήματα ὂντα ἀνόητα ϵι̑ναι.
• 15. Rep. 477 A. τò παντϵλω̂ς ὄν παντϵλω̂ς γνωστόν.