Having discussed, in historical and philosophical light, mankind’s discovery of the objective Infinite in nature, i.e., God, Creator (in Physical Religion), and the discovery of the subjective Infinite in man, i.e., the soul (in Anthropological Religion), Müller’s final course of lectures, delivered under the title Theosophy, or Psychological Religion, treats mankind’s discovery of the oneness of the objective God and the subjective soul which, according to the author, ‘forms the final consummation of all religion and all philosophy’ (p. viii). After a brief preface, composed in 1893 after the culmination of the lectures, the introductory lecture affirms once again the importance of the historical study of religion, claiming that this is the true ‘philosophy of religion’. The reader is reminded that all belief in God is predicated upon aspects of natural religion, not special revelation, and that the comparative study of world religions does not undermine but rather reinforces the uniqueness of Christ’s message and calls attention to the historical foundation for the Christian and for every other religion. In Lecture III, Müller explains that the historical relationships of ancient religions and philosophies are constituted by four things: common humanity, common language, shared ‘real’ history and neighbourhood or proximity. He discusses the relation between the religions of India and Persia, calling particular attention to the independent character, and so once again the scholarly primacy, of India’s religion and philosophy. The continuity between physical, anthropological and psychological religion is the subject of Lecture IV, which includes a recapitulation of what the author intends by his three divisions of ‘natural religion’ as outlined in his Gifford Lectures, and an explanation of the meaning of ‘psychological religion’: those attempts at discovering the relationship between the soul and the Divine, which, in Müller’s view of continuity and historical progress, occur historically subsequent to and necessarily presuppose physical and anthropological religion.

In close textual analysis, Lecture V, ‘Journey of the Soul after Death’, considers what the Upanishads teach about the relation of the soul to God and particularly about the return of the soul to Brahman. Eschatology, or ‘last things’, is the subject of Lecture VI (‘The Eschatology of the Avesta’), wherein Müller examines the basic similarities found in various eschatological legends with particular regard to the Avesta, and of Lecture VII (‘Eschatology of Plato’), which draws comparisons between the Upanishads and the mythological language of Plato, especially regarding the belief in metempsychosis, or the transmigration of souls. Lecture VIII, ‘True Immortality’, continues this eschatological thread. Müller points out the tension between conceiving of God as ‘personal’ (persons are naturally limited) and ‘impersonal’ (only persons can love, care); further, we, as persons, cannot conceive of ‘being’ in terms otherwise than personal and relational, given our limitations. Müller discusses this in relation to the Vedanta (the principal branch of Hindu philosophy) and its conception of Brahman, the highest godhead, as depicted in the Upanishads, and continues this in Lectures IX and X, ‘The Vedanta-Philosophy’ and ‘The Two Schools of the Vedanta’ (based on the teachings of Sankara and Ramanuja). The Vedanta philosophy rests on the fundamental conviction that the soul and Brahman, the Absolute Being, are one in their essence. However, according to the doctrine of Vedanta, Brahman itself cannot change or be transformed. Müller’s thorough analysis of Vedantist thought serves one aim: as theosophy, or psychological (immaterial) religion, is the highest evolution of natural religion; this historical manifestation of the religion and philosophy of India represents a high-water mark in world religion. ‘There is no room for anything outside the Infinite and the Universal, nor is there room for two Infinites, for the Infinite in nature and the Infinite in man. There is and there can be one Infinite, one Brahman only’ (p. 311).

The author turns his attention to the branch of Islam known as Sufism in Lecture XI, exploring the origin, morality and poetic language of Sufism and its connection with early Christianity. Sufism is satisfied with an approach of the soul to God, with the loving union of the soul and God, but this is quite different from the view that the soul and the Divine are one in the same, as we find in Vedanta. Also, as Sufism appropriates the language of the New Testament and makes reference to the Old Testament as well as to Jesus (Isaiah), Müller concludes that Sufism is influenced not only by Platonist and neo-Platonist philosophy but also most profoundly by Christianity. He writes: ‘Sufiism, short of its extravagances, may almost be called Christian….’ (p. 360).

Müller discusses Socrates, Plato, Aristotle, Heraclitus, Anaxagoras and Philo of Alexandria, a Jewish thinker around the time of the earliest Christians. For example, in his more allegorical interpretation, Philo considered the Logos a link between the world and its cause, between the soul and God; Plato is similar: the soul serves as a connecting link between the Divine and the human, between the invisible and the visible. But the Logos as a link between God and the world is most profoundly captured in Christianity’s faith in Jesus Christ as the Word (John 1) and Son of God, emphasizing the intrinsic similitude and the extrinsic difference of humanity and divinity. Müller then examines ‘Alexandrian Christianity’ in its Platonic and Aristotelian contexts in Lecture XIII. The view shifts to Plotinus, Clement of Alexandria and Origen. Clement, for whom there is no antagonism between religion and philosophy, considered the Logos, the Word, to be the mind and consciousness of God the Father, a bridge between the world and the Godhead. He recognizes this Logos in Jesus of Nazareth; ergo, when true self-knowledge of Jesus’ divinity has been obtained, sin becomes impossible for Jesus. This realization of the divinity of man, of the soul’s essential oneness with God, is, according to Müller, strikingly similar to the Vedanta. Origen too believed that the Logos in all its fullness was manifest in Christ as the perfect image of God. For Origen, all souls have fallen away and as punishment have been clothed in flesh for the duration of their time in the material world. Dionysius the Aeropagite (elsewhere called Denys the Aeropagite or Pseudo-Dionysius) is the focus of the penultimate lecture. First, Müller analyses the conception of the Logos in the Latin Fathers, paying special attention to Tertullian, before turning to Dionysius, a sixth-century mystic whose writings had a significant impact on medieval Christianity. The preeminent theologians of the Middle Ages were fascinated by the Dionysian corpus because they satisfied the human heart’s need to know that there is a relation between the human soul and the Divine. The final lecture is entitled ‘Christian Theosophy’. Müller continues, to some degree, his discussion of Christian mysticism, with additional attention to the German mystics, those Dominican and Franciscan monks who devoted themselves to the service of the people in fourteenth-century Germany. As emblematic, Müller invokes the mystical thought of Meister Eckhart; not surprisingly, the author considers Eckhart’s view consonant with the central idea of the Vedanta: by the removal of darkness, the individual soul can recover its true nature and realize its unity with the Divine—this is the bridge between the finite and the Infinite. Müller makes the connection between the Jewish Messiah and the Greek Logos, draws his discussion of mysticism to a close, summarises the goals of his four courses of lectures and concludes by thanking those responsible for the honour of serving as the inaugural Gifford Lecturer.