What is the Identity of a Thing? - Aristotle's Four Causes - Bk II Ch III from "The Physics"

What is the Identity of a Thing?

One of the central Pre-Socratic questions has to do with determining the identity of something, especially through the forces of change that nature seemed to put all things through. Is this a tree, wood, a bed, chloroplast, atoms, or a forest? Of course, Parmenides was famous for denying the reality of change, and thus, likewise, denying that things have identities at all beyond his notion of nature as the changeless unified sphere of being. And so how does one tell the identity of a thing given that there are many potential identities present in the current and actual identity? 

While Aristotle gives a very thorough discussion on this question, a core tenet of his explanation lies in his development of what he calls the "four causes." In so many words Aristotle has identified four classes or aspects of identity that go into making up the actual identity of what a thing is here and now. Thus they can also be called causes. He calls them the "material cause," "formal cause," "agent or efficient cause," and "final cause." 

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The Four Causes

The material cause refers to the prior parts which go into making up the thing in question. Another way of thinking about this is in terms of the "matter" of a thing being the prior set of identities which go into making a new identity. We can take the example of a birthday cake. In terms of the matter of the cake, we would have eggs, flour, water, sugar, oil, chocolate, etc. Each of these is itself a composite of its own form/matter with its own identity, but is becoming subsumed into something new, and thus functions as the matter of this new thing. Here's how Aristotle expresses it, "In one sense, then, that out of which a thing comes to be and which persists, is called 'cause', e.g. the bronze of the statue, the silver of the bowl, and the genera of which the bronze and the silver are species." Another way to phrase this would be to say that the material cause is the that from which something is. 

The formal cause, then, refers to the rational identity formed by the union of the prior material parts. Another way of seeing this is by asking about a thing's "what-ness." What is it? When the eggs, flour, water, sugar, chocolate, and other ingredients come together in the oven, we then rationally know that this is a new thing. It is no longer those ingredients, but the birthday cake. Not to get too technical, but for formal identity of a thing Aristotle is referring to an essential identity, not accidental ones. Here's how he phrases it, "In another sense the form or the archetype, i.e. the statement of the essence, and its genera, are called 'cases' (e.g. of the octave the relation of 2:1, and generally number), and the parts in the definition." The formal cause could be phrased as that which something is. 

The agent causes, sometimes referred to as the efficient cause, refers to the source or exterior cause of the identity of the thing. To return to the cake example, the efficient cause of the cake would be the baker who brought the ingredients together. Again, the point of efficient cause is to identify the main source of the thing, not accidental sources. For example, the maker of the oven is part of the causal network that goes into making up the cake, but he is not the efficient, or main cause, of the existence of the cake, but only an accidental one. It is the baker that is the essential source of the cake coming to be. "Again the primary sources of the change or coming to rest; e.g. the man who gave advice is a cause, the father is cause of the child, and generally what makes of what is made and what causes change of what is changed." Agent cause can be rephrased as that by which something is

The last aspect of determining a thing's identity has to do with the final cause. This is the purpose or intention for which something is. Now this is directly tired to the form of the thing, as the end for which something is, is determined by the core of what the thing is. "Again in the sense of end or 'that for the sake of which' a thing is done, e.g. health is the cause of walking about. )'Why is he walking about?' we say. 'To be health', and, having said that, we think we have assigned the cause.) The same is true also of all the intermediate steps which are brought about through the action of something else as means towards the end, e.g. reduction of flesh, purging, drugs, or surgical instruments are means towards health. All these things are 'for the sake of the end, though they differ from one another in that some are activities, other instruments." This could by expressed as the that for which something is.

Aristotle's Summary

He rephrases all four into a summary which can be helpful. He says: 

"All the causes now mentioned fall into four familiar divisions. [Material] The letters are the causes of syllables, the material [the causes] of artificial products ... the parts [the causes] of the whole, and the premises [the cause] of the conclusion, in the sense of  'that from which'. 

Of these pairs, the one set are causes in the sense of substratum, e.g. the parts, the other set [Formal] in the sense of essence -the whole and the combination and the form.-

[Agent] But the seed, and the doctor, and the adviser, and generally the maker, are all sources whence the change or stationariness originates, [Final] while the others are causes in the sense of the end or the good of the rest; for 'that for the sake of which' means what is best and the end of the things that lead up to it." 


1 - Aristotle. The Physics. http://classics.mit.edu/Aristotle/physics.html