I think it would be generally agreed that the two surest ways of getting into serious trouble in Christian circles in the first three or four centuries of the Church's existence were to engage in speculation either on the nature of Christ the Son and his relation to his Father, or on the mutual relations of the members of the Trinity. While passions have cooled somewhat in the intervening centuries, these are still now subjects which a Classical scholar must approach with trepidation—partly, at least, because the two disciplines of Classical Philology and Patristics, which were for so long so intimately connected, in the persons of a series of great scholars, are now so far removed from one another. I propose on this occasion to stick mainly to what I profess to know something about, that is the development of Platonic doctrine over the first few centuries AD, but I will inevitably be led from time to time into more dangerous speculations, and I trust I will receive due tolerance, as well as proper correction, where it is necessary.

The philosophy in Christianity is both inert and active. The late Greek metaphysics around which Christian doctrine first developed is Christianity's inert philosophical skeleton. Even if the dehellenizers could succeed in their efforts to remove it, Christianity itself would be unrecognizable without it. But the philosophy that is in Christianity actively, the enterprise of philosophical theology, is in it insecurely and only intermittently because it seems vulnerable to important religious and philosophical objections. As I see it, philosophical theology can be and actually has been successfully defended against those objections, and it is, I believe, incomparably the most interesting and important philosophy in Christianity—in fact, the only philosophy of more than historical interest there really is in Christianity.

Cui bono? Cherchez la femme! These ancient maxims offer counsel to the investigator of an unsolved murder or some inexplicable pattern of behaviour. They advise the pursuit of what has come more recently to be known as a form of lateral thinking. The puzzle may not best be solved by an intensification of the examination of the immediate data. The primary clue may lie out of sight somewhere further back. Financial advantage or sexual attraction, which does not show up as a feature of the immediate situation, may be the hidden motive of the traditionally male agent's actions. When that is recognized, the otherwise inexplicable phenomena may become intelligible.

The central doctrine of Christianity is that God intervened in human history in the person of Jesus Christ in a unique way; and that quickly became understood as the doctrine that in Jesus Christ God became man. In AD 451 the Council of Chalcedon formulated that doctrine in a precise way utilizing the current philosophical terminology, which provided a standard for the orthodoxy of subsequent thought on this issue. It affirmed its belief in ‘our Lord Jesus Christ, … truly God and truly man, … in two natures … the distinction of natures being in no way annulled by the union, but rather the characteristics of each nature being preserved and coming together to form one person’. One individual, one thing that is; and being a rational individual, one person. An individual's nature are those general properties which make it the sort of individual it is. The nature of my desk is to be a solid material object of a certain shape; the nature of the oak tree in the wood is to take in water and light, and to grow into a characteristic shape with characteristic leaves and give off oxygen. Chalcedon affirmed that the one individual Jesus Christ had a divine nature, was God that is; and it assumed that the divine nature was an essential nature.

Augustine's philosophy of being, the subject of my lecture, might be approached in two ways. In traditional terms, we might consider the question quid est esse, or alternatively the question quaenam sunt. This latter question is easily explained; it means, roughly speaking, what does the real universe contain or comprise, in a large and general sense. Material objects, of course, we can all accept; but what should be said about minds and spirits and the things with which they are concerned? The other question is more difficult to explain in simple terms. Suppose we translate it ‘What is being?’, we may seem to be asking a question about the word ‘being’; what is the sense which Augustine gives to this word? But in fact we shall discover a whole spectrum of senses. ‘Being’, for Augustine, sometimes appears to express the purely minimal notion of mere existence; but he also uses it as a powerful symbol to formulate his deepest reflections on the spiritual life and the nature of God.

In his great poem The Wreck of the Deutschland Gerard Manley Hopkins evokes the conversions of Paul and Augustine as two contrasting examples of the way in which God may intervene in human affairs:

With an anvil-ding

And with fire in him forge thy will

Or rather, rather then, stealing as Spring

Through him, melt him but master him still:

Whether at once, as once at a crash Paul,

Or as Austin, a lingering-out sweet skill…

‘In the beginning God created the heaven and the earth’ (Genesis 1.1). For millions of Jews, Christians and Muslims this has been a fundamental article of belief. Nor is it unknown in the classical Indian traditions. The Upanishads, taken by the orthodox to be ‘heard’, not invented, and to be verbally inerrant, state: ‘He desired: “May I become many, may I procreate” … He created (or emanated) this whole universe’ (Taittiriya Upanishad, 6). The belief that everything in the universe is brought into being by an act of will or desire on the part of one uniquely uncreated being is widespread and fundamental in religion. Historians of religion generally suppose that it is a rather late belief in the Biblical tradition, having developed from an earlier stage at which Jahweh was one tribal deity among others. By the time of the major prophets, however, the notion was firmly established that there is only one God, creator of everything other than himself. Christian theologians always seem to have had a great interest in conceptual problems, and the idea of creation has proved a very fruitful one for generating philosophical puzzles. Those puzzles are still of great theoretical interest, and I shall consider some of them with reference to the work of Augustine and, to a lesser extent Thomas Aquinas. Their views have been so influential that they may fairly be called ‘classical’, in Christian theology.

Elijah foretold evil for Ahab in the name of the Lord. ‘I will bring evil upon you; I will utterly sweep you away, and will cut off from Ahab every male, bond or free in Israel’ … but when he heard those words, he rent his clothes, and put sackcloth upon his flesh, and fasted and lay in the sackcloth, and went about dejectedly. And the word of the Lord came to Elijah saying ‘Have you seen how Ahab has humbled himself before me? Because he has humbled himself before me, I will not bring the evil in his days, but in his son's days I will bring evil upon his house.’

Christianity stands out among the three great Abrahamic religions in its willingness to make extremely precise dogmatic statements about God. The Christians who make these statements have generally regarded them as universally and absolutely true, since they are divinely revealed, or divinely guaranteed interpretations of revealed texts. Of course from the beginning there has not been universal agreement (to put it mildly) among Christians about what statements should be so regarded and how they should be worded: and the seriousness with which this need for dogmatic precision has been taken is shown by the way in which the inevitable disputes did not only involve theologians but the general body of Christians, and have led to divisions of churches, long continuing and flourishing mutual hatreds, and an overwhelming amount of theoretical and, where opportunity offered (i.e. where a Church party could get a secular power on its side), practical intolerance. Two areas of Church history which seem to me to provide particularly clear evidence of the incompatible verbal precisions demanded in dogmatic statements and the serious consequences of these demands are the Christological controversies of the fifth and sixth centuries and the Filioque dispute between East and West (though there is plenty of choice, and others may have other preferences). In both of these, theologians with a real and deep sense of the mystery of God often seem to an outside observer, in spite of their passionate assertions that this is not at all what they are doing and the rhetorical reverence of their language, to be arguing as if the God-Man or the Trinity were small finite objects which they had pinned down firmly in their theological laboratories and were examining under the microscope.

(1) If you would know God, you must not merely be like the Son, you must be the Son yourself.

With these words Meister Eckhart encapsulates the aim of Christian mysticism as he understood it: to know God, and to know God in such a way that the knower is not merely like Christ but actually becomes Christ, taken into the Trinity itself. Eckhart speaks frequently of this in his sermons.

Recent work on the subject of faith has tended to focus on the epistemology of religious belief, considering such issues as whether beliefs held in faith are rational and how they may be justified. Richard Swinburne, for example, has developed an intricate explanation of the relationship between the propositions of faith and the evidence for them. Alvin Plantinga, on the other hand, has maintained that belief in God may be properly basic, that is, that a belief that God exists can be part of the foundation of a rational noetic structure. This sort of work has been useful in drawing attention to significant issues in the epistemology of religion, but these approaches to faith seem to me also to deepen some long-standing perplexities about traditional Christian views of faith.

Most of us have probably heard Samuel Johnson's witticism about the reported proposal of an acquaintance to enter into a second marriage—‘the triumph of hope over experience’. Whatever that tells us about his friend's previous marriage, it tells us quite a bit about the popular understanding of hope. A similiar point was implied by J. B. Priestley when he referred to whisky distillers marketing faith and hope at twelve shillings and sixpence per bottle, and not for the first time G. K. Chesterton got it superficially wrong in defining hope as ‘the power of being cheerful in circumstances which we know to be desperate’.

The man generally known as Averroes—Muhammad Ibn Ahmad (c. 1126–98)—was a Muslim scholar from southern Spain who came to be regarded as one of the great authorities on Aristotle's philosophy. Medieval and even later philosophers in the Scholastic tradition referred to him simply as ‘the Commentator’ just as they referred to Aristotle himself as ‘the Philosopher’. Averroes' authority as an expositor was never wholly unchallenged and, in a purely historical context, the term ‘Averroist’ should strictly be reserved for those Aristotelians who followed the interpretations of Averroes rather than those of, say, Avicenna. Some of these interpretations, however, suggested beliefs that were inconsistent with acceptance of a Creator of the material world or with belief in a last judgment at which individual souls would be punished or rewarded for their life on earth. They suggested, rather, that the material world was eternal and that individual souls did not survive bodily death. This raised a general problem about what to say in the face of a conflict between faith and reason, between the teachings of the Church and the teachings of philosophy. Averroism became associated with a particular problem and with what was known as the ‘twofold truth’, according to which it is possible to admit the conflict and continue to profess a religious faith without abandoning or abridging one's commitment to philosophy.

Does photography leave everything as it is? Clearly not. It scalps Uncle George, as he stands at the church door, proudly, innocently, in the role of bride's father, and it decapitates his nephew James, who had until now been a head taller than any other member of the wedding group. It reduces to two dimensions, and to black and white, such solid three-dimensional objects as the Rocky Mountains and St Paul's Cathedral, such colourful scenes and sights as the Aurora Borealis and sunset in the desert.