f the discussion which has a direct bearing upon our subject. [Dynamis]
has been previously defined as "a principle of motion or change in
another thing in so far forth as it is another thing"[736]--that is, it
is fitted by nature to have motion imparted to it, and to communicate
motion to something else. But this motion wants a resting-place. There
can be no infinite regression of causes. There is some primary [dynamis]
presupposed in all others, which is the beginning of change. This is
[Greek: physis], or nature. But the first and original cause of all
motion and change still precedes and surpasses nature. The final cause
of all potentiality is energy or _actuality_. The one proposed is prior
to the means through which the end is accomplished. A process of
actualization, a tendency towards completeness or perfection ([Greek:
telos]) presupposes an absolute actuality which is at once its beginning
and end. "One energy is invariably antecedent to another in time, up to
that which is primarily and eternally the Moving Cause."[737]

[Footnote 735: "Metaphysics," bk. viii. ch. viii.]

[Footnote 736: Ibid., bk. iv. ch. xii.]

[Footnote 737: Ibid., bk. viii. ch. viii.]

And now having laid down these fundamental principles of metaphysical
science, as preparatory to Theology, Aristotle proceeds to establish the
conception of the Absolute or Divine Spirit _as the eternal, immutable
Substance, the immaterial Energy, the unchangeable Form of Forms, the
first moving Cause_.

I. _The Ontological Form of Proof_.--It is necessary to conceive an
eternal and immutable substance--an actuality which is absolute and
prior, both logically and chronologically, to all potentiality; for that
which is potential is simply contingent, it may just as easily not be as
be; that which exists only in capacity is temporal and corruptible, and
may cease to be. Matter we know subsists merely in capacity and
passivity, and without the operation of Energy,(energeia), or the
formative cause, would be to us as non-entity. The phenomena of the
world exhibits to us the presence of Energy, and energy presupposes the
existence of an eternal substance. Furthermore, matter and potentiality
are convertible terms, therefore the primal Energy or Actuality must be
_immaterial_.[738]

2. _The Cosmological Form of Proof_.--It is impossible that there should
be _motion_, genesis, or a chain of causes, except on the assumption of
a first Moving Cause, since that