Commentary
In the first half of the sixth century BC, Anaximander of Miletus (c. 610–546 BC), as reported by Aristotle (384–322 BC), identified the “boundless” or “unlimited” (τὸ ἄπειρον) with the divine (τὸ θεῖον) and treated it as the first principle from which all things come to be (Physics 3.4, 203b7–15).
Aristotle does not affirm Anaximander’s conception of the infinite as a divine, boundless substance; rather, he critiques it and replaces it with a distinction between potential and actual infinity, ultimately rejecting the existence of an actual infinite in favor of a finite, ordered cosmos governed by an immaterial first principle. Unlike Anaximander, Aristotle does not regard the physical universe as grounded in a boundless material principle; rather, he conceives the cosmos as a finite, ordered, and eternal whole sustained by an immaterial first cause. Aristotle believed in a finite universe, not a finite reality.
Aristotle was a philosopher of form, causation, actuality, and metaphysical dependence. He explains change as the movement from potentiality to actuality, argues that all change requires explanation, rejects an infinite regress of causes, and concludes that reality ultimately depends upon a Prime Mover / Unmoved Mover that is pure actuality, immaterial, and the final cause of cosmic motion. In contrast to Plato’s ordinary dualism, Aristotle’s position is a metaphysical dualism in which matter is not fully independent, but dependent on a higher immaterial principle.
Some scholars note a philosophical tension in Aristotle’s qualified dualism. While Aristotle explains change through the distinction between potentiality and actuality, the concept of pure potentiality raises a serious question: if it is entirely devoid of actuality, how is it meaningfully distinguishable from non-being? This is not Aristotle’s own explicit formulation, but rather a critical philosophical pressure point often raised in later interpretation of his metaphysics.
Aristotle, Physics 3.4
(excerpt)
“It is clear then from these considerations that the inquiry concerns the
physicist. Nor is it without reason that they all make it a principle or
source. We cannot say that the infinite has no effect, and the only
effectiveness which we can ascribe to it is that of a principle. Everything is
either a source or derived from a source. But there cannot be a source of the
infinite or limitless, for that would be a limit of it. Further, as it is a
beginning, it is both uncreatable and indestructible. For there must be a point
at which what has come to be reaches completion, and also a termination of all
passing away. That is why, as we say, there is no principle of this, but it is
this which is held to be the principle of other things, and to encompass all
and to steer all, as those assert who do not recognize, alongside the infinite,
other causes, such as Mind or Friendship. Further they identify it with the
Divine, for it is “deathless and imperishable” as Anaximander says, with the
majority of the physicists.
Belief in the existence of the infinite comes mainly from five
considerations:
(1) From the nature of time—for it is infinite.
(2) From the division of magnitudes—for the mathematicians also use the notion
of the infinite.
(3) If coming to be and passing away do not give out, it is only because that
from which things come to be is infinite.
(4) Because the limited always finds its limit in something, so that there must
be no limit, if everything is always limited by something different from
itself.
(5) Most of all, a reason which is peculiarly appropriate and presents the
difficulty that is felt by everybody—not only number but also mathematical
magnitudes and what is outside the heaven are supposed to be infinite because
they never give out in our thought.
The last fact (that what is outside is infinite) leads people to suppose
that body also is infinite, and that there is an infinite number of worlds. Why
should there be body in one part of the void rather than in another? Grant only
that mass is anywhere and it follows that it must be everywhere. Also, if void
and place are infinite, there must be infinite body too, for in the case of
eternal things what may be must be.
But the problem of the infinite is difficult: many contradictions result
whether we suppose it to exist or not to exist. If it exists, we have still to
ask how it exists; as a substance or as the essential attribute of some entity?
Or in neither way, yet none the less is there something which is infinite or
some things which are infinitely many?”
Reference:
Aristotle. (2009). The basic works of Aristotle. Modern Library. https://bookshelf.vitalsource.com/books/9780307417527