t;
for in that way only is it desirable (as shown above, AA. 1, 3). Now
a thing is said to be perfect if it lacks nothing according to the
mode of its perfection. But since everything is what it is by its form
(and since the form presupposes certain things, and from the form
certain things necessarily follow), in order for a thing to be perfect
and good it must have a form, together with all that precedes and
follows upon that form. Now the form presupposes determination or
commensuration of its principles, whether material or efficient, and
this is signified by the mode: hence it is said that the measure marks
the mode. But the form itself is signified by the species; for
everything is placed in its species by its form. Hence the number is
said to give the species, for definitions signifying species are like
numbers, according to the Philosopher (Metaph. x); for as a unit added
to, or taken from a number, changes its species, so a difference added
to, or taken from a definition, changes its species. Further, upon the
form follows an inclination to the end, or to an action, or something
of the sort; for everything, in so far as it is in act, acts and tends
towards that which is in accordance with its form; and this belongs to
weight and order. Hence the essence of goodness, so far as it consists
in perfection, consists also in mode, species and order.

Reply Obj. 1: These three only follow upon being, so far as it
is perfect, and according to this perfection is it good.

Reply Obj. 2: Mode, species and order are said to be good, and
to be beings, not as though they themselves were subsistences, but
because it is through them that other things are both beings and good.
Hence they have no need of other things whereby they are good: for
they are spoken of as good, not as though formally constituted so by
something else, but as formally constituting others good: thus
whiteness is not said to be a being as though it were by anything
else; but because, by it, something else has accidental being, as an
object that is white.

Reply Obj. 3: Every being is due to some form. Hence,
according to every being of a thing is its mode, species, order. Thus,
a man has a mode, species and order as he is white, virtuous, learned
and so on; according to everything predicated of him. But evil
deprives a thing of some sort of being, as blindness deprives us of
that being which is sight; yet it does not destroy every mode, species
and orde