There are many fascinating theologians of the early Middle Ages, but the doctrine of God remained basically Platonic. It found a particularly clear expression in the work of Anselm (1033-1109), whose ontological argument is considered elsewhere. In the course of that argument he propounded a definition of God as 'that than which nothing greater can be conceived' (2; Anselm 1965:117). He added that God is in fact 'a greater than anything that can be conceived' (15; ibid.: 137). This is an elegant definition of God's perfection. It proposes that the most adequate way for humans to think of God is to think of all the properties that it is better to have than not (such as power, knowledge, happiness and wisdom). Then think of them in their maximal possible degree (omnipotence, omniscience, supreme happiness and perfect wisdom). Think of the largest compossible set of the most valuable possible properties, enlarged to the maximal degree, united in one supreme reality. Finally, posit that God is infinitely more valuable than this being, which is the most valuable humans can think of.
This definition of God combines the 'way of eminence' (the cataphatic way) and the 'way of negation' (the apophatic way) which were important in early medieval theology, and are found expressed in the influential but unknown writer who called himself Dionysius (c.500). By the former, one ascribes all positive perfections to God. By the latter, one denies all properties of God, in the sense in which we understand them. Thus Dionysius calls God 'superjust' and 'super-wise', but insists that the essence of God remains wholly unknown. The philosopher may wonder whether the concept of a being which possesses all perfections is coherent, since many of them may be incompatible. Perhaps perfections (valuable properties) are results of merely subjective preference, so there can be nothing which all would agree on as a perfect being. Perhaps there is no maximal degree of most perfections (like happiness).
Perhaps the negative way, denying all properties of God, is simply vacuous. The Anselmian definition is not without its problems. Perhaps, however, there could be something which is so perfect in being that the greatest being we can conceive would be far less perfect than it, but would at least point in its direction. If so, theists would at least wish to assert that it must be identical with the God of Christian worship.
Meanwhile, the works of Aristotle, which rejected Plato's distinction of the intelligible and material worlds, were influential among Islamic theologians like Avicenna (Ibn Sina, 980-1037) and Averroes (Ibn Rushd, 1126-1198). The idea of God found in Aristotle's Metaphysics, Book 12, represents God as noesis noeseos, 'thought thinking itself'. For Aristotle, God is the 'prime mover', or 'unchanging cause of all change', an eternal and immovable substance which moves the outer sphere of the fixed stars, and so indirectly moves all things. It will live a life 'such as the noblest and happiest that we can live', so it will always be engaged in contemplative thought. Since it must changelessly think of what is best, and since the best possible thing is the Divine intellect itself, its object of thought must be itself. The activity of the prime mover consists in the contemplation and love of its own perfect essence. The outer sphere of the fixed stars is moved into an eternal circular motion by its love of the perfection of the prime mover; so 'the final cause moves by being loved, while all other things that move do so by being moved'. Aristotle's idea of a self-sufficient, self-contemplating unchanged first cause, which draws all finite things to itself by love, became very influential in Muslim, Jewish and later Christian theology.
Aristotle's God does not actively cause the world and does not even seem to know it directly. It knows and loves only itself, though the world is drawn to imitate it by love. The Muslim philosophers and Maimonides (1135-1204), the greatest Jewish medieval philosopher, naturally sought to modify this concept to allow for a doctrine of creation, of Divine knowledge and providence, with varying degrees of success. When Aristotle's works were translated from Arabic into Latin in the twelfth century many Christians also attempted to integrate their faith with this newly discovered system of metaphysics. The best known is Thomas Aquinas (1225-74), whose theology, although resisted at first, soon became a normative philosophical theology for the Roman Catholic Church.
In the Summa Theologiae, questions 3-11, Aquinas sets out his doctrine of God, beginning with the assertion that 'we cannot know what God is, but only what he is not'. A main reason for this is that God is absolutely simple. He is not composed of extended parts, and is therefore neither in time nor in space. He is not composed of form and matter, and is therefore 'pure form', an essence or intelligible nature which is self-subsistent. God's nature is identical with God's existence, therefore God is cesse suum subsistens', or Being-itself, not a particular thing which partakes of existence. Finally, being simple, God is totally different from any finite, composite thing, and nothing finite can be part of the unlimited reality of God. One might say that God is an 'unlimited ocean of being'. When humans try to think of God, they naturally think of a particular individual, entering into relations with finite things. All such thoughts fail to grasp the Divine infinity by making God finite. We cannot know what God is, because human concepts are not adequate to comprehend infinite being.
It may seem that nothing at all can be said of God. Yet Aquinas holds that some statements about God (e.g. 'God is good') are literally true. They are, however, analogically true. Such terms as 'good' apply to God, but not in the sense in which we understand them. This is because all perfections exist in God in a higher manner. 'Effects obviously pre-exist potentially in their causes' (Part la, Question 4, Article 2; Aquinas 1964:53), and God, as first cause, contains the perfections of everything, though in a simple, undivided way. To say that God is perfect is to say that God is purely actual, containing no merely potential being, having in himself the actuality of all things in an unlimited way.
As achieved and unlimited actuality, God is supremely desirable, and so can properly be called good. Indeed, God alone is supremely good, 'as being the first source of every perfection things desire' (Part la, Question 6, Article 2; Aquinas 1964:85). God is omnipresent, since all things exist solely by his substance, power and presence, and agents are present wherever they are active. God is immutable, since supreme perfection does not allow of increase or decrease, and since pure actuality excludes any potentiality in God. God is eternal, 'the instantaneously whole and perfect possession of unending life' (Part la, Question 10, Article 1; Aquinas 1964:135), since any existence of past, present and future in God would contradict his simplicity and infinity. God is one, since there cannot be two actually infinite sources of all being.
Aquinas' concept of God is that of an infinite reality, purely actual, with no element of potentiality, yet containing in itself, in an incomprehensible way, the perfections of all possible things, as their cause. This is about as far as one can get from an anthropomorphic idea of God as a disembodied person who is constantly interacting with, or intervening in, the world in response to prayers and new crises. A major philosophical problem is that the concept may be vacuous. An unkind critic may suggest that the idea of 'Existence itself existing is simply a nonsensical and ungrammatical construction, like saying that nobody in particular runs, but there is such a thing as 'Running itself which runs. There is also a tension, to say the least, between saying that we cannot know what God is, and saying that God is an all-perfect cause of the universe. If God is the cause of the universe, must he not be, in some sense, an individual (a substance), which Aquinas denies? Moreover, to claim that 'God is good' is literally true, but that the word 'good' does not mean what we think, is not very illuminating. If it does not mean what we think, what is the point of saying it?
As well as problems of internal coherence, there are problems about how such a God can relate to the created universe. It has been noted that Aristotle's God neither knows nor creates the universe. Can Aquinas' God do either? Aquinas says that 'Things other than himself [God] sees not in themselves but in himself (Part la, Question 14, Article 5; Aquinas 1964:19). This must be so, if God, being immutable, cannot be changed by knowledge of what is other than himself. God is simple, however, so that in knowing himself, God knows his essential nature, which cannot change. It looks as though all things are wholly determined to be what they are by the Divine will, which is identical with the Divine nature. God being what he is, other things cannot but be what they are. God could have created a different universe only if his nature (which is identical with his existence) had been different. That is, God could have created a different universe only if he had been a different God. If this is so (and of course Aquinas would seek to deny that it is), this God can only create this universe—which contradicts a dogma of the Catholic faith.
The problems are even worse with the Christian doctrines of Incarnation and Trinity. If God is utterly simple, how can there be three hypostases in God? If no finite thing can be part of God, because of his absolute infinity, how can the human nature of Jesus be identical with the eternal Word? If God is completely unchanged by what happens in the world, how can he suffer on the cross, respond to prayer or act in believers through the Spirit? I do not suppose that such questions are unanswerable, but they do pose great difficulties for Aquinas' account. The most basic question is whether God is to be conceived as a personal individual who enters into real causal relations with the universe, or as a purely actual, simple and infinite unity of all perfections, bearing no real relation to anything outside itself (Part la, Question 6, Article 2; Aquinas 1964:87), yet being the pattern, source and goal of all finite realities. It is the latter conception which characterizes the classical Christian tradition—though, surprisingly, it does not seem to be well known outside philosophical circles.
The late medieval period was rich in philosophical disputation. William of Ockham (1290-1349) is often taken to be the major exponent of 'nominalism', the school that denies that universals or Forms are real. Taken to its logical conclusion, this makes a Platonic concept of God as Pure Form impossible, though William did not go so far. He did, however, insist that God is not subject to any necessity, even of his own nature. By sheer fiat, God directly wills individuals to exist; the whole universe, including its natural and moral laws, could have been quite different. God is pure omnipotent will, and is not subject to any logical or moral constraints. God cannot therefore be criticized or assessed on philosophical or moral grounds. This is an idea that appealed to some of the sixteenth-century reformation theologians, who rejected all philosophical approaches to the question of God, and insisted on simply accepting the Bible as final.
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