Dr William Large

In this lecture, we shall look at the work of Aristotle.  We can not hope to cover the whole of this work, which extended over numerous topics ranging from political theory to astronomy, rather we shall focus on his metaphysical theories and especially in the manner in which we might contrast them to Plato’s.  In one sense, we might say that Aristotle and Plato offer us the two alternatives of Greek philosophy: rationalism and empiricism, though we do need to be careful here, since these are terms that are introduced later into philosophy and would not have been known by Aristotle himself. Platonist is a rationalist who arrives at his metaphysical doctrines through the pure application of reason, whereas Aristotle is the dogged empiricist who arrives at his ideas through observation and research.  This at least as been the view that has been handed down to us by a long tradition.

It is obvious that Aristotle does depart from Plato’s theory of forms, but it vastly underestimates the complexity of this metaphysics by labelling it empiricist as opposed to Plato’s rationalism.  In this lecture, we shall look at one of Aristotle’s criticisms of Plato’s theory of the forms, and then at three aspects of his own metaphysics, the notion of substance, which is the heart of this metaphysics, the four types of causality, and the distinction between potentiality and actuality.

Plato has, as we have seen, has the basic insight that knowledge of the world cannot be simply based on the sense-perception of individual things, but requires, at least to the extent that we can claim true knowledge of things, as opposed to mere doxa, the existence of concepts or universals.  Thus, to understand this or that individual thing, I must possess the concept of this thing in general.  To grasp the box as a box, I must understand the meaning of the word ‘box’.  What is strange in Plato’s theory is that this universal box is a separate existing entity, though of course not a sensible entity, for then it would be an individual thing, but a mental entity which he called an Idea, which pre-exists this or that individual box, and gives to this or that individual box its essential nature.

Now it is the separateness of the universal from the particular that Aristotle rejects.  What we know is the world and we know this world through experience.  What we know through experience are individual things and it is in knowing these individual things that we come to know what universals are.  Universals are merely what is common to individual things, and therefore cannot be said to have an independent existence from these individual things.  I know what the universal ‘box’ means, because I have come across many boxes in my experience and have noticed that these boxes all have something in common which can be named by the word ‘box’, but this does not prove at all that something like a universal box exists separately, even as a mental entity.

The fact that all that exists for Aristotle are individual things is further underlined in his theory of substance.  The idea of substance, or ousia in Greek, is the cornerstone of Aristotle’s thought, just as the theory of forms is the cornerstone of Plato’s thought.  Aristotle first arrives at a theory of substance in a work called the Categories.  The subject matter of this work is the possible predicates of an object.  Aristotle is not interested about what can be predicated of an object individually, this wall is white, for example, since there would be many predicates like these as there would be objects, but what can be predicated of objects in general.  Another way of thinking about this is that you can see the difference in talking about the properties of different individual objects from the properties that every object must have to be an object at all no matter what particular kind of object it might be.  Aristotle believed that there were 10 such categories:

1)      what substance

2)      how much - quantity

3)      of what kind - quality

4)      related to what  - relation

5)      where - place

6)      when - time

7)      rest - position

8)      have - state or condition

9)      to do active - Action

10)  to suffer passive - Affection

            The most important of these categories is that of substance, for substance is the primary mode of being for Aristotle, for science and philosophy talks about ‘what is’ first of all, and only then about the other nine categories (in fact in the Metaphysics, Aristotle will say that the topic of ‘first philosophy’, by which he means the discussion of basic principles, is the question of the ‘what is’ or the question of being).  The examples of substance Aristotle gives in the list of categories are ‘man’ and ‘horse’.  Now these examples of are like Platonic forms in that they are universal.  Is this what Aristotle thought primarily what ‘what is’ is, a network of forms or universals?  But this would make him too much of a Platonist.  In fact what is real for Aristotle are not universals but individuals.  ‘Man’ and ‘horse’ for Aristotle are only secondary substances. What are primary substances are individual things such as this man called Socrates or this brown horse.

From a logical point of view, we can say that a substance for Aristotle is something that can be a subject of a predicate.  This is why substance is primary, for it is that thing to which are attached predicates.  In this sense universals are secondary for Aristotle because they only have a meaning when attached to or predicated of individual things, but cannot be said to have any existence separate of these individual things.  I predicate ‘man’ of Socrates, but it is Socrates who exists and not man in general.[1]

            The relation between an subject and predicate also allows Aristotle to explain change in the physical world.  With Aristotle change or ‘becoming’ again becomes central to philosophy, as it was for Heraclitus, and is not rejected for the timeless nature of being, as is the case in Plato and Parmenides.  In fact, being itself is understood as becoming, for ‘what is’ is now understood as individual things which undergo change, rather than as universal forms which are fixed for all time and impose unity and order on individual things which are downgraded to mere copies.  How does Aristotle understand change?  He understands it through the basic opposition of potentiality and actuality.  Something that exists can change into something that it was not previously.  A can change to B.  Aristotle argues that A cannot change to B if it does not in some sense contain B within in.  Thus, in nature there is no sudden change from one state to the next.  We say that B is potentially in A, or that A actualises its potential B when it actualises itself in the state B.  But Aristotle’s theory of potentiality and actuality is slightly more complex than that, for he says that an actuality is always prior to a potentiality.  A is not potentiality B unless it can come actually to be B, if A can never be B then it cannot be said to have the potentiality of being B.  But something cannot come to be from a potential, something actual must cause it to move from A to B.  Thus the acorn has the potential to become an actual oak tree, but only because there is a cause, whether external or internal which leads it to this development.  This leads us to Aristotle’s theory of causation.

            We might say that the question of substance tells us what something is, whereas the question of cause tells why something is what it is.  For Aristotle, there are four kinds of cause that he names as follows: material cause, efficient cause, formal cause, and final cause.  All these different kinds of cause tell us why something is the kind of thing that it is, and not some other kind of thing.  Cause here means types of explanation and should not be confused with the modern conception of cause that contains a notion of one body affecting another body.  The Aristotelian notion of cause is not the same as the cause and effect.  Let us briefly then describe the different types of cause in Aristotle.

            The material cause is that by which something is made, its matter so to speak.  The formal cause is that by which this matter is formed into some particular thing.  It is that by which shapeless matter becomes a particular individual thing distinct from other particular things, or sharing the same properties with those things that belong to the same set.  The efficient cause is that which sets in motion the initial development by which matter is determined by a particular form.  The final cause is the end of this process of development by which something becomes what it is.  In other words the final cause is the realisation of the formal cause. 

            Perhaps the best way to think about the difference meanings of cause in Aristotle is to use an example.  Suppose we ask ourselves why is it that there is an oak tree growing outside of our window.  There must be a seed from which the oak tree has grown, which has the potential to become an oak tree, this is the material cause.  The oak tree must have followed a definite path of development which belongs to the essence of oak trees, this is the formal cause.  The seed of the oak had an origin, which was the parent oak tree, this is the efficient cause, and finally there is a final stage where the development of the oak reaches its proper realisation, this is the final cause of the oak tree.

            This is only a brief summary of the main elements of Aristotle’s philosophy, and it in no way captures the whole.  For example, we have said nothing about his theology (though again he would not have used this word) that had an enormous effect on the development of Christian thought, nor his theory of logic.  What we can say about Aristotle, however, is that for the first time, in Greek philosophy, we have a systematic philosophy, and it is perhaps this that is the most important legacy of his thought.

[1] It can be argued the nature of substance in the Metaphysics is not the same as the explanation of substance in the Categories.  In a more substantial lecture this difference would need to be investigated.

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