[Footnote 724: Schwegler's "History of Philosophy," pp. 120, 123.]

The opposition of matter and form, with Aristotle, corresponds to the
opposition between the element of _generality_ and the element of
_particularity_. Matter is indeterminate; form is determinate. Matter,
abstracted from form, in thought, is entirely without predicate and
distinction; form is that which enters into the definition of every
subject, and without which it could not be defined. Matter is capable of
the widest diversity of forms, but is itself without form. Pure form is,
in fact, that which is without matter, or, in other words, it is the
pure conception of being. Matter is the necessary condition of the
existence of a thing; form is the essence of each thing, that in virtue
of which substance is possible, and without which it is inconceivable.
On the one side is passivity, possibility of existence, capacity of
action; on the other side is activity, actuality, thought. The unity of
these two in the realm of determined being constitutes every individual
substance. The relation of matter and form, logically apprehended, is
thus the relation of POTENTIALITY and ACTUALITY.

This is a further and indeed a most important step in the Aristotelian
theology. Matter, as we have seen, after all, amounts to merely capacity
for action, and if we can not discover some productive power to develop
potentiality into actuality, we look in vain for some explanation of the
phenomena around us. The discovery, however, of energy (energeia), as a
principle of this description, is precisely what we wanted, and a
momentary glance at the actual phenomena will show its perfect identity
with the eidos, or form.[725] "For instance, what is a calm? It is
evenness in the surface of the sea. Here the sea is the subject, that
is, the matter in _capacity_, but the evenness is the _energy_ or
actuality;... energy is thus as form."[726] The form (or idea) is thus
an energy or actuality (energeia); the matter is a capacity or
potentiality (dynamis), requiring the co-operation of the energy to
produce a result.

These terms, which are first employed by Aristotle in their
philosophical signification, are characteristic of his whole system. It
is, therefore, important we should grasp their precise philosophical
import; and this can only be done by considering them in the strictest
relation to each other. It is in this relation they are defined by
Aristotle. "Now energeia is the