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Aristotle's case for a prime mover


To: Scott B.
From: Geoffrey Klempner
Subject: Aristotle's case for a prime mover
Date: 21st November 2011 12:03

Dear Scott,

Thank you for your email of 10 November, with your essay for the University of London BA module on Aristotle, in response to the question, 'In what manner is Aristotle's god explanatory?'

This question can be taken in two senses: in what manner did Aristotle intend his conception of god to be explanatory? and does he in fact succeed in that intention?

It needs to be said that Aristotle does not set out his argument for a prime mover in such terms. According to the argument he lays out, the existence of a prime mover is necessary (as you observe, in order to account for the fact of 'motion'), and that is why we should believe it. The extent to which it 'explains' anything is arguably an additional question. One possibility which is not ruled out from the start is that the existence of a prime mover is necessary, as a matter of logic, but the conception of a prime mover does not 'explain' anything (in any sense in which we would understand the notion of explanation), and is not intended to.

Finally, there is the question, which you do raise, whether the theory as presented by Aristotle holds together, whether it is in fact internally consistent. As you note, with regard to Aristotle's 'stellar intelligences' moved to action teleologically by their contemplation of the prime mover, 'Something that is both immaterial and has potentiality does not fit easily into Aristotle's scheme of things.' This point would have been worth elaborating on.

According to you, the short answer to the exam question is that Aristotle's god is intended to be explanatory by being the final cause of motion rather than an efficient cause. However, there is a problem with the way you lay the argument out, contrasting the Aristotelian prime mover with the 'first cause' of the cosmological argument.

A potted version of the cosmological argument -- which is effectively the version you give -- would be that the chain of causes and effects cannot go back indefinitely. There must be a first event, the first cause, which acts as the beginning of the chain. This picture fits the story of Genesis, but it is limited because it assumes from the start that the universe must have a beginning in time. It is not, however, necessary to assume this.

The god of Judeo-Christian theology is not an entity which exists in time. god views the universe 'sub specie aeternitatis', under the aspect of eternity. He stands outside the causal series. It is perfectly possible, therefore, that the causal series stretches back indefinitely ('to infinity') while god is the ultimate, timeless, cause or creator of the entire series. Why would you still need a 'first cause' in this sense, if we allow that there is no first event in time? An analogy which is sometimes given would be that of a object, say a glass chandelier, suspended on a long chain. Each link in the chain is held in place by the link above it. Let's say the links are indestructible, capable of bearing any weight. If you asked what was holding the chandelier up, would it be any answer to say, 'There is no first link, because the chain stretches upwards to infinity'? Clearly not.

Later, in your essay, you do note that an explanation is needed for the continued existence of the universe at any given moment in time. This was in fact a view which Descartes argued for, and which Spinoza took to show that the only thing that can be genuinely regarded as a 'substance', as not depending on anything else for its continued existence, is god. Ordinary objects have no magical existential inertia. The very fact that an object exists, at any given moment, requires a sufficient explanation, which is not provided merely by the fact that it existed at some previous moment.

Armed with this conception, the defender of the cosmological argument can happily ignore the question whether or not the universe has a beginning in time. Either way, it's existence now depends on god's creative action.

However, this picture, of god the ultimate creator of the infinite series of events stands in stark contrast with Aristotle's prime mover which, as you say, has no knowledge of the imperfect, empirical world. It follows that the existence of a prime mover cannot explain *everything*, in the way that the Judeo-Christian god does. Consequently, there is no 'problem of evil' for Aristotle.

So what we have is an ultimate teleological explanation, rather than a causal explanation. But this teleological explanation is limited by the fact that it does not apparently connect with the things of this world -- the kinds of teleological questions that arise when we consider the form of a horse or a tree, or a man.

Why should the universe continue in existence? At the end of your essay you offer the suggestion that a 'slight shift in the meaning of the word 'creator'' might lead us to regard Aristotle's prime mover as accounting for the material universe continuing to exist from one moment to the next. This is in fact the Cartesian (and Judeo-Christian) view outlined above. But can we attribute the idea to Aristotle?

As a matter of brute fact, there is motion, and to account for this Aristotle argues for a necessary cause of motion. Given such a necessary cause, there *must* continue to be motion. The material universe cannot cease to exist, otherwise motion would cease to exist, contradicting the argument for a prime mover. But this does not make the prime mover a 'creator' in any sense that we would recognize. The prime mover accounts for the fact that the universe exists, leaving open the question *how* it exists.

All the best,