wo species, one of which is not subordinate to the
other. But in respect of those things which are superadded to the
substance, one thing can be contained under different species. Thus
one and the same fruit, as to its color, is contained under one
species, i.e. a white thing: and, as to its perfume, under the
species of sweet-smelling things. In like manner an action which, as
to its substance, is in one natural species, considered in respect to
the moral conditions that are added to it, can belong to two species,
as stated above (Q. 1, A. 3, ad 3).

Reply Obj. 2: The end is last in execution; but first in the
intention of the reason, in regard to which moral actions receive
their species.

Reply Obj. 3: Difference is compared to genus as form to matter,
inasmuch as it actualizes the genus. On the other hand, the genus is
considered as more formal than the species, inasmuch as it is
something more absolute and less contracted. Wherefore also the parts
of a definition are reduced to the genus of formal cause, as is
stated in _Phys._ ii, 3. And in this sense the genus is the formal
cause of the species; and so much the more formal, as it is more
universal.
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EIGHTH ARTICLE [I-II, Q. 18, Art. 8]

Whether Any Action Is Indifferent in Its Species?

Objection 1: It would seem that no action is indifferent in its
species. For evil is the privation of good, according to Augustine
(Enchiridion xi). But privation and habit are immediate contraries,
according to the Philosopher (Categor. viii). Therefore there is not
such thing as an action that is indifferent in its species, as though
it were between good and evil.

Obj. 2: Further, human actions derive their species from their end or
object, as stated above (A. 6; Q. 1, A. 3). But every end and every
object is either good or bad. Therefore every human action is good or
evil according to its species. None, therefore, is indifferent in its
species.

Obj. 3: Further, as stated above (A. 1), an action is said to be
good, when it has its due complement of goodness; and evil, when it
lacks that complement. But every action must needs either have the
entire plenitude of its goodness, or lack it in some respect.
Therefore every action must needs be either good or bad in its
species, and none is indifferent.

_On the contrary,_ Augustine says (De Serm. Dom. in Monte ii, 18)
that "there are certain deeds of a middle kind, which can be done
with a goo