Reflections On Aristotle’s Prime Unmoved Mover

The summit of Aristotle’s examination of “first philosophy” occurs in Book XII of his Metaphysics. Chapters 1-5 of Book XII reiterate Aristotle’s examination into the nature of thinghood (an inquiry which had previously appeared in Aristotle’s Physics). Thinghood is a kind of whole (not a part of a whole) representing the sources as well as the causes of independent things. Thinghood delineates the world. There are three kinds of thinghood: the material which is a ‘this by coming forth into appearance’ – which is perceptible and exists in the world of motion and destruction (i.e. a human composed of skin and bones and so on). The second is the nature of a thing and the active condition into which it comes (a living human who is growing and aging and so on). Lastly, is the particular kind of thing, such as “Socrates” or “Callias.” Curiously, Aristotle does not mention the fourth of thinghood that is mentioned in the Physics: the final cause, or the controversial teleological cause (perhaps the fourth cause is discussed as the prime mover, itself, in the course of the book). Aristotle then discusses types of changes in the world (referencing his argument in the Physics) which include the material, and the two types of being: potency and being-at-work. Another is motionless such as Platonic forms or mathematics. In examining the idea of change and motion, Aristotle strives to discover one or multiple motionless origins of motion and also, therefore, time (according to Aristotle, motion and time are co-existent, which is contra Einstein).

In Aristotle’s Metaphysics as in the Physics, the world around us is the result of causes -for example, an oak tree drops an acorn, the acorn falls into the ground, it grows into a tree, and the cycle continues. However, taking into account an evolution of life over time, Aristotle wonders if the causal lineage of all things can be traced back to one central source that is the catalyst for all future causes. He says: ‘All things come into being by the motion of some prior being, such as by art or nature, or else by fortune or chance’ (1078a).

In Book XII chapter 6 of the Metaphysics the central argument of the prime mover begins. Aristotle suggests, for the sake of the argument, that both motion and time are continuous. According to a causal cosmos, however, there must be a source of motion that is being-at-work-staying-the-same, and is also ever-lasting like the stars in the sky (whose motions are considered to be everlasting by Aristotle). Aristotle believes that if we simply retrace the lines of causes it will inevitably lead back to a primary source (or perhaps multiple primary sources). However, no single human being can possibly trace all causes in a lifetime, therefore the act of retracing the causal lineage of things is fundamentally an activity of the intellect.

Aristotle poses his central question at the crux of his argument in Book XII: “For how will thing have been set in motion, if there were not some responsible thing at work?” For Aristotle, material requires a craftsman and menstrual fluid requires male seed, a revealing claim which he claims in Chapter 6. For “nothing moves at random,” but rather things are moved by force, intelligence, or something else -and what is that something else? Aristotle leaves this door open in suggesting the existence of other possibilities for the origins of motion. From here, Aristotle seems to shy away from explicitly confronting the difficult question of his inquiry and instead he points us to the problem, and then posits a certain teleology to the cosmos. Up until this point, Aristotle has offered a glimpse into the difficulties of approaching the question of being qua being.

The prime mover of all future causes initiates motion “in the manner of something loved.” Not unlike a philosopher, the prime mover is a lover of the intellect. It is a thinker contemplating thought itself which is revealed to be the cause of all being and motion. Since the prime mover is composed of thought thinking itself, it can have no knowledge of future causes or beings that have resulted from its continuous motion. The prime mover is everlasting ‘like a god’ but it is motionless and unmoved, unlike a god. The prime mover cannot have magnitude since all finitude depends on some form of magnitude and the prime mover has no finitude because it is everlasting (this discussion of magnitude is further discussed in Aristotle’s Physics). The prime mover instills one everlasting motion in the shape of a sphere, like the circular movements of the planets which are also everlasting (here in the discussion, Aristotle’s Prime Mover starts to resemble Plato’s master craftsman in the Timaeus dialogue). Like the stars and planets there are likely multiple prime unmoved movers as the movements of the wandering planets suggest the activity of thought thinking itself, as well. Thus, the planets who adorn the night sky are an imitation of the prime mover’s act or acts of intelligence that unwittingly cause the cosmos.

Aristotle concludes Book XII with comments on theology (theology is only invoked after philosophic inquiry has been fully explored). Aristotle labels the inheritance of the gods as “myths” for the “persuasion of the masses” and the clarity of the god’s role in relation to the prime mover is left ambiguous. However, Aristotle’s prime mover shares certain characteristics in common with latter monotheistic theology which is developed over many centuries after his death. Here, Aristotle ends his inquiry with a brief comment. He cites the poets (Homer) and suggests that the cosmos would be best governed by one single intelligible whole in a Parmenidean sense (in the same way that the concept of number is whole and not divisible according to ancient Greek mathematics). Aristotle cites the Iliad at the end of Book XII (“a divided sovereignty is not good; let there be one lord” Iliad Book II, 204) -a quote which is in reference to Odysseus’s reformation of the chaotic Achaeans into a well-organized army against Ilium. The “lord” being referenced by Aristotle in the Iliad is the master political leader (i.e. Odysseus) and the reference in connection to the cosmos opens the door to the possibility of a divine intellect which has not created the world, but rather confers upon things a unique, delineated thinghood (these claims will later be revised to fit with European Christian orthodoxy by Thomas Aquinas some fifteen hundred years later).

To recap, Aristotle initially began his book as an innocent inquiry into the nature of things. He then proceeded into a lengthy dialectical or conversational discussion about ontological questions. Through the investigation, Aristotle slowly dismissed certain commonly held opinions and offered a new and higher perspective on speaking about being qua being. By the end, Aristotle’s exploration concluded with several possibilities examined, particularly in regard to a possible origination of motion and time, and a commonly-held “myth” was reaffirmed at the end for the sake of what is orderly and good (similar to the form of Plato’s “Myth of Er” at the conclusion of the Republic).


For this reading I used Joe Sachs’s monumental translation of Aristotle’s Metaphysics.

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