LECTURE #3: Plato, Aristotle, al-Farabi

I. Plato

The earliest version of the cosmological argument occurs in Book X of Plato's The Laws. It is noteworthy how well Plato's argument fits the general pattern:

1. Everything of type X has a cause.

2. There is something of type X.

3. For some reason (namely, Y), the series of causes of an X must terminate in a first cause.

4. This first cause can be identified with God.

In the last lecture, I identified four dimensions of variation: focus, rationale, temporality, and modality. At this point I'd like to add a fifth: closure. Closure concerns the argument for point 4 of the general schema: what are the divine characteristics of the first cause that can be supported by the argument, and how are the inferences to these divine attributes supported? Let's go through each of the five dimensions of variation, and see what we can find in the text that is relevant to each.


Plato starts with the existence of motion, more specifically, the locomotion (change of position) of matter. What Plato is doing in this passage is called reduction ad absurdum -- reducing his opponents' position to absurdity. In this case, the opponents are the materialists of his day, both atomists (like Democritus) and non-atomists (like Empocles, who believed that matter consisted of continuous fluids). The materialists espoused a principle of evolution that is very similar to that of Darwinism or neo-Darwinism: random movements of matter over time give rise to stable and sometimes very complex structures, including those of living organisms and human society. The materialists denied the need to postulate any sort of principle or power outside those inherent in matter.

Since the materialists depend on the existence of motion, Plato can legitimately take that as one of his starting-points or premises. Moreover, the materialists also agree that all motion is caused: they accept that the search for causes is the business of science.


Plato argues for the necessity of a first cause by distinguishing between self-generated motion and transmitted motion. Self-generated motion is not caused by any other motion. Transmitted motion is merely the transference of motion from one thing to another. There must first be motion before that motion can be transmitted. Therefore, an infinite regress of transmissions, with no origin, is impossible, since there would be no motion for the transmissions to transmit (pages 424 and 425).

What Plato seems to be saying is that if B causes C to move by transmitting motion from A to C, then B is not really a cause of C's motion -- it is merely a conduit through which A causes C to move. Consequently, a series of transmissions, with no first element, would not really be a cause of motion at all. Hence, if motion is really caused, it must have a first cause.

As we shall see, this rationale is repeated by many later thinkers, including Aristotle and Aquinas. It's plausibility depends on the fact that we find the idea of an infinite causal regress, with no first element, very odd. This seems a plausible, but not a conclusive argument, for the first-cause principle.


Plato seems to be working with a diachronic (through-time) conception of causation. He concludes that Soul is older than matter, that it is the first thing. This at least suggests that causes are earlier than their effects, so the first cause is the earliest thing. However, Plato does not try to describe a creation-in-time of the world of matter-in-motion, so we should be cautious in drawing too firm a conclusion here. In any case, his argument does not seem to depend on any particular view of the relation of causation and time.


It is difficult to say whether Plato thinks of causes as necessitating their effects. The spontaneity by which souls generate motion suggests a degree of freedom and contingency, but Plato (like other ancient Greek philosophers) does not explicitly endorse a doctrine of the freedom of the will, so again we must be cautious. Plato later argues that there must be different kinds of souls, some good and some bad, to explain the presence of both good and evil in the world. This suggests that the actions of a soul are necessitated by its nature.


There are two attributes of God that Plato reaches almost immediately: animacy (life) and immateriality. Plato argues that the First Cause of motion is very similar to living humans and animals, since in both cases we see self-generated motion. Unlike inanimate matter, living organisms move spontaneously, at the direction of their desires and rationality. The first cause moves spontaneously, so it is probably alive. This seems to an argument from analogy (God is like a living thing), or perhaps an argument to the simplest explanation: why postulate two different kinds of self-generated motion when one will do?

A subtle move that Plato makes is from living thing to soul. He concludes that the First Mover is an immaterial soul, not a material thing at all. What Plato seems to have in mind is something like this: matter, by its very nature, is only a passive transmitter of motion. To say that some matter (a living body) moves itself spontaneously is really to say that there is present in the matter some immaterial principle (soul) that is the cause of the motion.

Although Plato refers to "God" in the singular, his reasons for postulating a single God are fairly weak. In fact, Plato thinks that there are many souls, some greater than others. He seems to think that there is a supreme or first Soul, that is the source of the greatest and most fundamental motions, such as the revolution of the fixed starts around the earth (we will see Aristotle develop this idea further). Plato concludes that this First Soul is rational and morally good, because of the rationality and beauty of the motion it causes. In effect, Plato makes a transition to a form of the design argument, inferring the intelligence and goodness of the designer from the perfection of the design.


A clear strength of the argument lies in its simplicity and austerity. It includes no fanciful inventions or dubious hypotheses. This simplicity accounts for the longevity and timeless relevance of the argument: although many details reflect the scientific and religious ideas of Plato's culture, the argument itself seems to stand independently of those cultural influences. Another striking thing about Plato's argument is its originality, both in form and substance. Plato attempts to address fundamentally important theological questions from the perspective of common sense and reason. Moreover, he does so in a way that is remarkably independent of specifically religious experiences or impulses.

On the weakness side of the ledger, it has to be said that Plato's rationale for the necessity of a first cause is under-developed. It moves much to quickly to satisfy the skeptic. Moreover, Plato's closure of the argument seems relatively weak, since we have little reason for believing in a single First Cause, and no reason to think that the cause is infinite or eternal.

II. Aristotle

Aristotle's version of the cosmological argument also fits the general pattern. In these notes, I will be making some reference to Aristotle's arguments for the Unmoved Mover in his Physics, as well as in Book Lambda of the Metaphysics (the passage in the Supplement).


The focus for Aristotle argument is motion, in a more general sense than the locomotion of Plato's argument. Aristotle recognizes four kinds of change: change in quantity, quality, relation (including position), and substantial change (creation and annihilation). The term "motion" (kinesis) encompasses the first three kinds of change. So, motion includes locomotion, but also change in quantity (increasing and diminishing) and quality (growing hotter or whiter or smellier). Unlike Plato, Aristotle does not begin by accepting (even for the sake of argument) the assumption of materialists that all physical change is explainable in terms of the locomotion of atoms or other microscopic bits of matter.


This is a controversial point. Some argue that Aristotle is assuming a synchronic model of causation: there must be now a cause of any motion that is occurring now. Causes of motion must be simultaneous with the motion. On this view, the present motion of the sphere of the fixed stars around the earth is the cause of all motion on earth at this very same moment. Movement is transmitted instantaneously from the outermost sphere to every other moving thing.

However, there is some evidence for the contrary view. In Book Lambda 3 of the Metaphysics (before our selection) Aristotle states that the factors that produce change are things that have come into being before. This seems to imply that causation is diachronic -- that causes are earlier than their effects. On this view, if the sphere of the fixed stars were (as is in fact impossible) to stop revolving, motion in the heavens and on earth would gradually wind out, but would not come screechingly and immediately to a halt. Any present motion could be traced back, through a finite number of steps, to some past phase of the revolution of the stars, but not to the present movement of that sphere.

One unique feature of Aristotle's argument is his belief in the eternity of the physical, space-time world. Aristotle argues that time has no beginning or end, since the notion of a beginning of time is illogical. If A is the first moment of time, then before A there would be no time. But the phrase 'before A' presupposes that there is an earlier moment, B. Thus, we are forced into the contradiction of saying that B is and is not a moment of time. In addition, Aristotle argues that motion is eternal and continuous. For some reason, Aristotle thinks that the idea of a finite period of time during which nothing changes is absurd. Perhaps Aristotle thinks that time is constituted by the relations of earlier and later holding between distinct events or episodes in the world's history. If nothing is happening, there are no distinct episodes, and so no possibility of one thing being earlier or later than another.

What is interesting about Aristotle's argument is that, despite his belief in the eternity of the world, he still believes that there must exist a first cause of all motion, an "unmoved mover". One could use Aristotle's argument as part of a dilemma: either the world is eternal or it is not. If it is not eternal, then clearly there must be a first cause that brought it into being. If it is eternal, Aristotle's argument purports to show that there still must exist a first cause of the world's eternal motion. Either way, a first cause must exist.

There is one respect in which Aristotle's argument deviates from the standard form of the cosmological argument. Aristotle does not start merely with the premise, "there is motion" (premise 2 of the standard form). Instead, he starts with the premise "necessarily, there is motion". He argues that not only does motion exist now and at every point in time, it must exist at all times. This is because both an end to time and a perfectly quiescent period of time are supposed to be impossible. This is important for Aristotle's argument, since if motion is necessary, and there is a first cause of motion, that first cause must itself be necessary, and it must be necessarily active. These features of Aristotle's argument have a profound influence on the inferences about the First Cause that Aristotle draws.


Aristotle's argument for the existence of a first cause is similar to Plato's. He distinguishes between unmoved movers and intermediate movers (Lambda 7, p. 258). Intermediate movers have no power in themselves to move anything -- there power to move depends entirely on the unmoved mover behind them. Consequently, an infinite regress is impossible, since all of the members would then be intermediate movers, and none would have any power to move.

In the Physics, Aristotle offers another argument against infinite regresses. If there were an infinite causal regress, there would exist infinite motion in finite time, which is impossible. This seems to assume that the infinite regress cannot extend infinitely far back into time, and also that it is impossible for there to exist at any finite period of time, any process or activity that involves actual infinity. We might look to empirical physics for support of these propositions.


In general, Aristotle does not seem to think that causes necessitate their effects. However, the Unmoved Mover is a special case. Since motion is necessary, the Unmoved Mover must exist, and it must at all times produce motion. On page 259, Aristotle makes an important distinction, between necessity-as-compulsion, and simple necessity. Nothing compels the Unmoved Mover to exist or to cause motion -- He is an absolute first principle, unaffected by anything else. However, the unmoved mover exists and acts with necessity, in the sense that it is impossible that the mover not exist or not act. Simple necessity is a condition that "could not be otherwise."


Aristotle argues that the Unmoved Mover must be immaterial, since if He were material, He could move other things only by moving Himself, which would raise the necessity of explaining the motion of the Mover. Like Plato, Aristotle quickly concludes that this immaterial being must be a mind.

The most interesting inference about the Unmoved Mover that Aristotle draws concerns the issues of potentiality and actuality. As I mentioned last time, Aristotle explains the possibility of enduring substances that endure through time by distinguishing potentiality and actuality. An enduring thing is called a (primary) substance. Each substance has a fixed essence, which determines which properties or attributes it can possess, either potentially or actually. Aristotle uses the word "potentially" in two different ways. Sometimes it means "merely potentially". In this sense, I must be either actually pale or potentially pale, but not both. At other times, it means "either actually or merely-potentially". In this sense, I am at all times potentially pale -- sometimes actually so, sometimes merely potentially so. I will use the word "potentially" in the second sense. The potential properties of a substance are constant over time: what changes is which of these properties are actual and which are not. These variable properties are called "accidents". All change is change in the accidents of a substance.

Aristotle argues that the First Cause must be a being of "pure act", a being whose nature it is to be actual. This seems to mean that there is for the First Cause no distinction betweeen potentiality and actuality. The First Cause has no accidents: every property it has, it has essentially. This entails that the First Cause is immutable, since it lacks exactly that feature that explains the changeability of other substances.

Aristotle constructs a model of the sort of mind that might meet this admittedly strange condition of pure actuality. He describes a mind that eternally contemplates itself, and only itself. Intellectual contemplation is an activity, but it is one that does not entail change. A being enjoying perfect knowledge of itself need experience no variation or undulation at all. Aristotle describes this self-thinking mind as enjoying perfect happiness. Finally, Aristotle suggests that the First Mover causes motion in the world by being immediately present to certain subsidiary intelligences (such as the celestial intelligences responsible for heavenly movements), and by inspiring these intelligences to emulate the perfection and happiness of the Unmoved Mover.

Finally, there can be only one Unmoved Mover, since the unmoved mover is immaterial, and there can be only one immaterial being. Matter is that which distinguishes one individual of a given kind from another: Socrates is different from Plato because they are composed of different matters. Since the unmoved mover is immaterial, there is nothing that could differentiate him from any other unmoved mover. Hence, there can be only one.

If we ask, could there be a succession of different Unmoved Movers, one at a time, Aristotle responds (in the Physics) by arguing that in that case the creation and destruction of the successive Movers would itself require an explanation, since it is necessary that at each moment there should exist a Mover. This underlying cause of the succession of Movers would then be itself the one and only First Mover. This argument is important, since it extends the cosmological argument from the case of motion (kinesis) to that of substantial change (creation and destruction of substances). This means that even if there were no motion at all, but only substantial change, Aristotle argument for a First Cause would still go through. (We will see this picked up the medieval philosophers.)

There is another argument implicit in Aristotle's. Suppose that we suggested that the First Mover was not a being of pure actuality, but one in which there was real potentiality. Suppose we argued that, although this First Mover has the potentiality of non-action, it is nonetheless the case that it acts at all times, and does so necessarily. Aristotle would certainly respond that the necessary action of such a potentially inactive being requires some further causal explanation. This is so, even though, by our hypothesis, the potentially inactive Mover never changes. This suggests that there is a more fundamental argument beneath the surface of Aristotle's argument, one for which the focus is actualized potentiality, and not change per se.

III. Al-Farabi

Al-Farabi was a tenth-century Arab philosopher who had a profound effect on medieval philosophy, Muslim, Jewish and Christian. He translated and wrote commentaries on Aristotle's works and on many of those of the Neo-platonists. Al-Farabi synthesized or combined the ideas of Aristotle and Neo-platonist philosophers, setting the direction of most subsequent medieval philosophy.


Al-Farabi's most significant contribution to the cosmological argument is a dramatic shift of focus from motion or change to contingent existence. By "contingent", I mean "actual but not necessary". Anything that exists but need not have existed is contingent. Al-Farabi argues that there are such contingent existences (including all those things subject to change, or to creation or destruction), and that all such contingent existences must have a cause.

Al-Farabi introduces into philosophy a crucial distinction: that between "essence" and "existence". This distinction is inspired by some comments by Aristotle in his Posterior Analytics, in which Aristotle says that we must distinguish "what a thing is" from "that it is". The first is its essence, the second its existence. For instance, Socrates has an essence -- humanity. In addition, Socrates has an existence. Socrates' existence is that happening or eventuality whereby humanity is made real or concrete in the person we call "Socrates".

Al-Farabi's distinction is an extension or generalization of Aristotle's distinction between potentiality and actuality. Aristotle describes every substance as composed of matter and form (or essence). In Aristotle's system, the matter is the aspect of potentiality, and the form is the aspect of actuality. For example, a mass of bronze is potentially a statue. It becomes actually a statue when it takes on the appropriate form or essence. The form/essence actualizes one of the potentials of the matter. What al-Farabi does is to subject Aristotle's form/essence element into two components: essence and existence. The essence of the statue is itself only potentially real: it becomes actual when it is impressed upon a mass of bronze, resulting in an existing statue. The essence of humanity is capable of being made actual in many different places and times: it has a wide-ranging potentiality for existence. Actual existence is the expression of this essence in particular matter at a particular time.

Al-Farabi's distinction, if accepted, means that we could have many different immaterial beings. Each being (say, an angel), would be the realization in existence of some essence. Without matter, we might have a problem supposing that one essence could be shared by many different entities, but we could imagine a situation in which there are many different essences, each realized by a different immaterial existent.

Al-Farabi's distinction is supposed to be real distinction in the nature of things, not a mere verbal or mental distinction. In other words, al-Farabi assumes the real existence of universals (types, properties, essences). The essence of Socrates is one thing, his existence is another. Both are real, neither is simply the invention or projection of our own minds. All of the ordinary things we encounter are like this: there is always a real distinction between their essence and their existence. Whenever this real distinction occurs, al-Farabi assumes, there must be a cause that explains why this particular essence has been actualized into this particular case of existence.


Al-Farabi's rationale is clearly of the anti-regressive type. That is, he asserts that an infinite causal regress is impossible. Unfortunately, he is not very explicit about why this is so.


Al-Farabi clearly adopts a synchronic view of causation. He says that contingent beings (beings whose essence and existence are distinct) remain contingent, even after they come into existence. What he seems to mean by this is that there remains a need to find a causal explanation of the continued existence of contingent beings. Some first cause must explain what preserves the world in being at every moment.


Al-Farabi's starting-point is that of simplicity. The first cause must be a very strange kind of being -- one for which there is no distinction between its essence and its existence. The first cause is the only being for which this is the case. It is wholly other from anything we have contact with in sense experience -- there are no analogies that will help us to understand how God's essence could be the very same thing as its existence. The argument forces us to this conclusion, but it provides us with no understanding of how such a thing could be possible. But, al-Farabi would urge, so what? Why should we expect that the fundamental reality should be comprehensible to our finite intelligence?

Since essence and existence are inseparable for God, there is no distinction between God's being possible (the reality of His essence) and His being actual (the reality of His existence). This means that, if God exists at all, He exists necessarily. Moreover, God is uncaused and inexplicable. In order to cause God to exist, one would have to cause His essence to be realized in existence, but this is impossible, since His essence is inseparable from His existence. Where there is no distinction, there can be no combination, nor any explanation of how the combination came about.

According to al-Farabi, God is infinite, since every finite being is limited, and every limitation is a kind of cause. It is a little unclear what al-Farabi means by saying that every limit is a kind of cause. It may be that he means that every limit is obviously contingent, and every contingency is caused. Or, perhaps his point is that limitation involves either potentiality (being capable of being more or less) or complexity of essence (having an essence that includes a specific limit). However, God's essence is absolutely simple (since it is identical to God's existence, which is a simple thing), and there can be no potentiality in God, since any potentiality would entail contingency, which would in turn entail the presence of a cause of God's accidents.

Since there is no potentiality in God, God is immutable.

There can be only one God, since if there were two, they would have to differ either in essence or accident. God has no accidents, so the two Gods would have to differ in essence.