Reading : Western Philosophy II.2 "Individual Substance"

Aristotle is characterised as presenting a very common-sense view of the world. He was a scientist of sorts, and did much work investigating natural phenomena, attempting to classify different animals into species etc.. In some ways his metaphysics reflects this approach.

This text contains some of Aristotle's ideas about what are the fundamental units of reality - what things are real? Whereas Plato sees the world that we live in as being populated by objects that are imperfect shadows of their ideal forms, Aristotle comes from the other direction, and regards substance as the most real thing: in this view, the idea of a "dog" only exists because we have experience of many actual dogs and so we invent a category "dog" to describe them.

In explaining his point of view, Aristotle uses the idea of predicates and substances. One dictionary defines a predicate as "a property, characteristic, or attribute that may be affirmed or denied of something". The "something" here is what Aristotle would call a substance, and he argues that since predicates can only exist in the context of their application to a substance, then it is substance which must be fundamental.

When we say a sentence such as "the lorry is green", the lorry is the subject and is green is the predicate. Substances can only ever appear in the subject position, never the predicate (you might have a predicate in the subject position though - e.g. "five foot eleven is a good height to be").

Aristotle groups his predicates into ten different classes, or categories. For example:

• [secondary] substance ("what is it?")
• quantity ("how big is it?")
• quality ("what colour is it?")
• place ("where is it?")
• action ("what is it doing?")
• passion ("what is being done to it?")

Aristotle says that it is substance which is fundamental, explaining that:

• The way we use language seems to indicate that "things" are fundamental, and are characterised by properties/events etc..
• You can't have a property/event/quantity whatever unless you have a substance to apply it to.
• Substances can remain although their properties can alter (e.g. a man's hair can change from black to grey, and disappear altogether)
• A substance can have many different properties
• Properties can have contraries (this doesn't just mean opposite to, it can also mean different to, i.e. a property contrary to "height of five feet" would be "height of five feet two inches"). But you can't have a contrary to "Socrates"
• Properties can be quantified (e.g. Socrates' height). But substance doesn't have more or less (Socrates can't be any more or less than Socrates)
• When we view the world, we see substance before qualities "Every substance seems to signify a certain 'this'". We see a tree, we don't see a "green"

Aristotle divides properties into two types: essential and accidental. An essential property is something that will always apply to a substance: for example an essential property of Socrates is his body. An accidental propery is something that may change or disappear, for example the colour of Socrates' hair.

Some questions that might be asked of this approach are:

• At what point do we draw the line between a substance and a set of components? E.g. if Socrates is a substance, does that mean his arm isn't? Or his fingers? How far can we break things down before they stop being substances?
• Can a substance that has no properties exist?

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