The question of universals, of what they are and how they are related to particular and immediate knowledge, continued in philosophical debate. On the two extreme sides of the debate are the nominalists and the realists (or essentialists). In the 17th Century Hobbes revived the nominalist position as stated much earlier. He argued that the word man does not refer to a universal existence but is merely a general name for all particular men, and we form the meaning or definition of this word by what we observe of particular men. The knowledge of man is formed by an abstraction or generalisation, but there is no real essence of man in particular men. Realists after Aristotle had argued that a universal essence, such as man, is indeed a real kind of substance, or at least a substantial form in Aristotle's sense, that is somehow embodied and expressing itself through matter and motion. The most extreme realist might argue that all universals, or general ideas, are real substances expressing through particulars.

Yet it could be argued, though, that Aristotle never actually thought that man was a real essence. He said that the essence of man is the rational intellect. But it is uncertain whether he meant that the underlying essence of all individual men is a man substance, unless one means that this underlying substance is the rational intellect. Once we abandon the odd notion of a man substance, or worse, a radical monism that all individual men are really one identical man, a more moderate notion might be plausible - that all individual men share the same functional capacity of rational intelligence, that all men share this same final form of potential perfection. So however odd it might be to believe that all particular men possess a real essence man, it is not so odd to believe that all particular men possess the same real and essential rational intellect, at least in potential. This would be a better interpretation of Aristotle's meaning.

A certain confusion may be afoot. Some general terms may not be essences in themselves, but rather nominal terms implying some real essence. The particular object in front of me is a cup, not because it possesses the essence cupness, but because it possesses the common essence of all true cups. My ball is not necessarily a ball because of possessing ballness, but because it is round. Round is the real essence, not ballness. And if roundness is not an essence apprehended in the world of particular things, then how do I know that something is round? This kind of question puccled philosophers.

Some universals do seem to be just general words, though implying necessary properties of things in order for the universal to be true in an assertaion. Yet at some point in anaysing universals, we will eventually arrive at the most simple, unanalysable universals or general properties. So if we find the most simple properties of particular things, these will be general characteristcs, such as roundness or bounciness, which are not the same as exact measurements, and yet these simple universals seem to be shared by many things.

Philosophers tried to figure out the relation between universals and particulars. In his translation of Aristotle, Porphyry (233-304) posed three questions about the relation between generic-general ideas and specific observations: 1) Do genera or species essences really exist in nature, or are they merely mental constructions? 2) If they are realities, are they material or immaterial? 3) Do they exist apart from sensible things, or in them?

Boethius (480-554) attempted to answer these questions with a moderate realism. He began by distinguishing two different ways in which the mind forms concepts, either by composition in which ideas are put together, or by abstraction in which the mind abstracts out from particular things their universal essences. The abstracting mind acquires the universal ideas, so in this sense the universals are mental concepts. Yet these concepts reflect the existence of universal essences. The genera or species exist in particular things, yet are also universals thought by the mind. So universals exist in things and also in the mind when the mind discovers them. In answer to porphyry's second question, they exist materially in things and immaterially in the mind. And to the third quetion, they exist in things but apart from things in the mind. We are able to think of universals separate from sensed bodies. This position, though, is still a realist position on universals, for they do exist in things apart from our mental apprehension. Yet this position is not fully Platonist, since these universal essences are believed to exist in the plurality of particulars, not above and beyond them.

Opposite to realist views is a nominalism maintained by Roscellinus (1050-1125), who argued that only unique individuals exist in nature, while species and genera are not real in nature but are merely general terms. A universal is merely a name (nomen - hence nominalism), a composition of letters and a vocal sound, and logic is only a relation of words, not real things. As an example, he said that the Christian 'Trinity' was just a word, and that there was nothing common to the beings of this Trinity but the word.

St. Anselm (1033-1109) defended the doctrine of the Trinity from nominalist thinking. He argued that the Trinity must be three distinct beings yet one essential divinity. For one not believe that all three divine beings are essentially one, would imply three unrelated divine powers and no unity in the universe. And to believe that there can be only one divine Being would suggest that Christ is not divine, unless there is no Father and Son. Debates about the Trinity had been going on of course for years, but Anselm realised from Roscellinus that it was logically tied to the debate about universals, such that the true doctrine of the Trinity recquired a realism regarding universals. Thus, each member of the Trinity must share the same identical essence, for otherwise They would have no divine relation to one another. In a similar way, each human being must share the same identical essence, if they are to have the same essential meaning and purpose in God's creation. Otherwise, our unrelatedness and essential separateness would mean that the same divine rules and plan of salvation would not apply to everyone. Anselm went on to other arguments from this realist position - that universal words stand for real essences outside of the mind- and that words such as good, perfect and wise refer to real essences of God and exist somewhat in this world too.

Peter Abelard (1079-1142) took a middle position between realism and nominalism. To begin with, he distinguished a universal name from an individual name in that universals apply to many individuals or separate things. The same relation exists between universal ideas and particular knowledge. He then argued that the nominalist position is wrong, because a universal idea has objective ground by its necessary relation to particular knowledge and individual existences. Thus, a universal is not merely a subjective notion without any relation to real things. It has objective ground because the very notion of a universal is abstracted from our observations of individual things. We abstract universals from individual things, so universals and general properties are grounded in, and dependent on, our sensory knowledge of individual existences.

Yet Abelard also argued against the strong realist position. He said that universals are not real substances or essences of individual things. The universal is certainly dependent on particular things, yet in itself it is no more than a concept and not something really existing in the world. It is abstracted from the world, but it is not in the world. So, the universal is not something actually found in the world, or in particular existences, as if the universal were a real substance of things.

What then are we abstracting? We are not getting the universal out from the world. It isn't there. Neither are we perceiving the universal in the world. Again, it isn't there. Abstraction, for Abelard, is a mental act of concieving a universal concept from perceiving similarities in the world. Similarities are found in the world, not universals. So, we recognise a similarity between things because of how these things really are, and this similarity is the basis for any notion of a universal. This is why many individuals are classed together by one universal, because we perceive a similarity in those individual things. So this recognised similarity is the real ground of universal concepts, rather than a uniform substantial essence.

Thomas Aquinas (1225-1274) agreed very much with Boethius' moderate realism regarding universals. He said that universals are found in particular things and abstracted from these things after experiencing them. So they are in things but also in the mind from our abstraction. Yet he also maintained that universals exist before and apart from individual things as Ideas in the mind of God. So some things share an identical universal as known in the mind of God. Nonetheless, we can intelligibly see the universal in particular things, that is, we can abstract the universal from the particular, sensed objects. Unlike Plato, he believed that the mind has no innate ideas of which to recollect. Rather, the mind must acquire universal knowledge from the world of sense experience, or from particular phenomenon, as Aristotle maintained. We have to study this world in order to understand metaphysical and universal truth, for there is no knowledge without sense experience. God has innate knowledge of all universal truths, but not man, for man must acquire this knowledge from his experience in this created world.

In contrast to the moderate realism of Aquinus, William of Ockham (1280-1349) maintained a nominalism, saying that a universal is nothing existing outside of our minds. Universals are mere words that we use to logically organise the world of our experience. This nominalism was also tied to Ockham's argument against Aquinus' position that God holds in His Divine Mind the Universal Ideas and that when humans realise universals they are participating in God's Mind. Ockham argued, instead, that God must have willed this existence into being with no prior Ideas. Things are as they are, not because God has perfect ideas in mind - of which this world approximates - but simply because God makes the world whatever He wants. Our world is simply a matter of God's Will or Power. So God does not creating from any prior or eternal Ideas. He's just making what we wants to make. This theological view was then tied to Ockham's view of universals, in that universal ideas could not exist, neither in God's Mind nor in God's creation. The universals can only be notions in our human minds, formed by our desperate attempt to organise the world in our minds and simplify this vast mystery of God's creation. So the mind organises individual things in general classes by general names, and the universals are nothing but these general names.

But why are some things organised together by one name, while other things are classed together by another name? Ockham's explanation is similar to Abelard. He says that classifications, using universal terms, are formed by our natural observation of similarities or likeness between things. The word man is simply a general name that we can apply to this individual person and that individual person, because they and others are similar. They don't actually share any uniform essence, and they aren't really the same in any way, but we perceive a similarity - partly because of our natural need to understand some order in this world of unique particulars. So, the mind does not know with certainty anything more than individual things and sensory knowledge, yet the mind is able to use general names in order to logically organise particular sense-knowledge according to observable similarities.

Ockham had heard enough complex and involved explanations for how things are, and too many complex justifications for the Christian doctrine. So he felt that philosophy needed to cleer away the extraneious defences of religious doctrine and describe reality in the most concise way. Creation is ultimately a mystery and we know not the reason of God, but our own reasoning mind can try to understand things as best it can. So our understanding should be as simple and clear as possible. Let us content ourselves with the simplest explanations, according to our direct experience of how things are. Thus, what can be explained more simply by less principles, or less general theory, needs no more explanation. This prescription became known as Ockham's Racor.

Anselm attempted to prove God's existence by rational thought. He pointed out that we compare things for their perfection, and no matter how perfect anything is there is always a greater perfection beyond our grasp. He believed, as Plato, that if things are good or perfect, in relative degrees, there must exist an absolute good or perfection - beyond the relative, and eternal in itself. If there is no eternal idea of good and perfect, then why would anyone even have thoughts of the good and perfect? Also, we need to account for the existence of relative good, which must be caused by something absolutely good - God. Also, if there are greater and greater degrees of goodness and perfection, there must be a final greatness of goodness and perfection. And this is God.

Anselm later presented a purely rational argument in favor of the existence of God, without any reference to our experience of the world. It is known as an ontological argument, and the gist of the argument is as follows. First, a definition of God is put forth, that God is 'That which nothing greater can be thought'. God is That which is greater than thought can possibly know. The question is, then, if That really exists. The fool, or disbeliever, denies God's existence. Yet by doing so he is involved in a great contradiction, because he is saying that he knows 'That which nothing greater can be thought' does not exist - even though That is greater than can be thought. Even the disbelieving fool is admitting that he knows the meaning of 'That which nothing greater can be thought', so he is already admitting that his intellect can comprehend the existence of God. He is admitting that he can comprehend a Being greater than can be thought.

Anselm's argument might be viewed as strange, if not confused. Is the fool admitting a positive belief, or is he merely showing that God is at least logically possible as That which is greater than thought can possible know? By Anselm's definition of God, we could not possibly refute God's existence since God is beyond our thought, but it is difficult to see that the fool is admitting God's existence by simply comprehending the meaning of Anselm's definition. One might know what he means by God, as 'That which nothing greater can be thought', but does this understanding of meaning necessarily imply the actual existence of That? It seems that Anselm is equating an admitted knowledge of meaning, or the meaning of a proposition, with an admission of the propositional truth or the existence of what is meant. He seems to be confusing 'a knowing of what God is' with 'God is'.

So Anselm's argument was not convincing to many of his peers. It was argued that the fool could not possibly have knowledge of God in this manner, since no one can possibly know 'That which nothing greater can be thought' - for That is beyond thought. Anselm attempted to prove God's existence by reasoning or thought, but if God is greater than thought then this is impossible. The only way to know God, for most theologians, was simply faith or divine revelation, so for many religious thinkers Anselm showed himself to be the real fool, thinking that reason could prove the existence of God.

Thomas Aquinas

Thomas Aquinas in the later part of the 13th Century brought his philosophical intellect to questions of theology. St. Augustine earlier had brought a Platonic philosophy to Christianity, and this was still the dominate theology, but Aristotle had become more favored by newer philosophers involved with the emerging natural sciences, so Aquinas set out to make use of Aristotle's system in theological questions. An Aristotelian philospohical approach was different from the Platonic approach, in that arguments were made from natural observations rather than arguments from reason alone. Aquinas thought that theology and a philosophy of science could agree in many ways, though theology necessarily diverted from philosophy in its practical prescriptions for man's spiritual salvation. So science specialises in understanding the material world of nature, while theology specialises in understanding the spiritual world and fulfilling man's spiritual needs.

Aquinas took great interest in the natural world, and he believed that it could show us absolute truths as well, even though the deeper spiritual truths could only come from revelation, scripture and faith. Since the natural world is God's creation, Aquinas trusted that principles and order found in nature must reflect God's wisdom and rational plan. So the knowledge of natural principles, or laws, reflects God's knowledge though in lesser degree. In fact, this correspondence between God and His natural creation became the ultimate metaphysical principle in Aquinas's philosophy. This meant that science and the observation of nature is a legitimate pursuit for the serious theologian, as an important means for understanding God and His Reason.

Man himself, and his inherent capacities, are micro reflections of God's Being. The human being is not God, of course, nor a perfect reflection of God, but God can be understood by analogy to our own possible qualities. Thus we can ascribe to God the same higher qualities known of man, such as wise and loving, yet Aquinas is careful to insist that such qualities as wise and loving are not exactly the same for God and man. Our higher qualities are only proportionate in relation to God's, and God cannot really be known in His full reality. At best, we can only apply weak analogies to God, based on what we know of ourselves. But these analogies are the closest we can come to God's truth, so they are significant. This gives us some knowledge of God from the outside, but we still cannot know what it really is to be God.

Also, Aquinas describes the universe as a great chain or hierarchy of being, known by either reason or revelation, whereby the angels are fixed intelligences, principles or powers. Below the angels are human beings, and below humans come the animals, plants, and finally the four elements of fire, air, water and earth. These segments are not completely seperate, though, but interlocked and sometimes merging into one another, which gives a unity and continuity to the hierarchy.

Aquinas was also concerned with the proof of God, in defence from skeptics and atheists. He made five arguments to logically demonstrate the existence of God, though, in contrast to Anselm, he began from our ordinary knowledge of the world, rather than how we think about God and the world. His arguments are obviously inspired by Aristotle. They all have the following pattern. Beginning from our sense experience of the world, we naturally know that every object and event requires a cause. Nothing comes from nothing. And since every thing must have a cause, these causes must also have causes, and so on and so on, until ultimately we must suppose the existence of a First Cause, God. To explain what we know from experience of this world, God must exist as the ultimate cause.

His first argument is called the Proof from Motion. It is evident from our sensory experience that many things are in motion, and we know that anything in motion must have been moved by something else. And this something else moving another thing must itself be in motion, which means that it must have been moved by something else preceeding it in time. This logic of motion keeps regressing backwards, until we finally have to suppose the existence of a First Mover moving other things but not in motion itself. This First Mover could not in itself be in motion, since this would presuppose a prior mover, and we'd be back to the need for a first explanation. Therefore, there must be a First Mover able to move things, but not in motion itself and not moved by anything else. Also, this Mover is not simply at rest, with the potential of being moved. It is not a potential motion, but rather the actualiser of all motion. This is God.

Next is the Proof from Efficient Cause. Every event must have a cause and no event can be its own cause. Nothing can come from nothing, so any thing that exists, or any event that happens, must be caused by something else, which in turn must be caused by something else, and so on and so on. So there ultimately must be a First Cause, just as there must be first parents to the whole series of birth in the human kingdom. In fact, there must be a First Cause to all that exists. This is God.

The third is the Proof from Necessary versus Possible Being. Everything or anything existing in this world is also possible to have not existed. That is, it is possible that any thing might never have existed, and it is also possible for any thing to go out of existence. Therefore, nothing is a necessary being but only a possible being. But if everything is just a possible being, how do we explain this mere possibility coming into existence? A mere possibility of existence could only come into existence by a power that is itself not just possible but necessary. In other words, we cannot just suppose that possible beings came into existence by another possible being, as though one possibility could bring other possibilities into existence. For if this were so, there would have to be a further possibility making it all actual. Ultimately then, we have to suppose something first prior to all possibility, or to all possible beings, that will bring the possible into actuality. This would have to be an ultimate actuality that is not just a possibility - something that is not just a possible being but a necessary being which has always been actual. This is God.

Fourth is the Proof from the Degrees of Perfection. From experience we find that some people are more good, wise and loving than others. But we could only make such comparisons if there were a maximum to these qualities. There must be an absolute maximum ideal, or perfection, to which beings are relatively compared. From this, Aquinas argued that the maximum perfection, or most perfect potential form in any genus, must be the cause of all near perfections in the genus, just as fire being the maximum of heat is the cause of all relative heat. Ultimately, then, there must be a cause of all relative goodness and perfections; and this God.

The last argument for God is the Proof from the Order of the Universe. We can observe that parts of the body, which do not possess intelligence, behave orderly. They generally achieve ordered ends, so we can only suppose that they are designed to achieve this order because they obviously are not behaving in a random way. A greater intelligence must be behind all of the ordered behavior that we observe. That is, things which carry out an ordered function must be directed by an outside intelligence. Therefore, some great intelligence must be directing the order of things; and this is God.

In ethics, Aquinas accepted most of Aristotle, except that man is in need of spiritual salvation and should pursue this religious end, as well as his natural perfections and balance. Man achieves his natural ends by the power of reason, but his religious ends can only be known by revelation and scripture, and can only be achieved by the grace of God. Also, human freedom is significant and is a prerequisite for a truly moral act. Good action by instinct is not moral action. Moral action must involve the freedom to choose amoung alternatives, involving the power of will to make choices. So God gave us freedom, and thus the possibility of immoral action, because unfree or deterministic acts could never show our love of God and never really prove our virtue. Thus, the one who accomplished good from free choice, in his love for God and goodness, is distinguished in God's eyes from those who chose otherwise. The way of salvation is, then, by our own choice or free will, though we still need God's grace and help. Salvation thus depends on our own choices and our act of free will, rather than being determined by God's Will, though God helps those who pray and seek higher guidance.