. 2: Further, in differentiating powers, habits and acts in
respect of their objects, we consider chiefly the formal aspect of
these objects, as we have already explained (I, Q. 77, A. 3).
Therefore diversity of habits is taken, not from their material
objects, but from the formal aspect of those objects. Now the
principle of a demonstration is the formal aspect under which the
conclusion is known. Therefore the understanding of principles should
not be set down as a habit or virtue distinct from the knowledge of
conclusions.

Obj. 3: Further, an intellectual virtue is one which resides in the
essentially rational faculty. Now even the speculative reason employs
the dialectic syllogism for the sake of argument, just as it employs
the demonstrative syllogism. Therefore as science, which is the
result of a demonstrative syllogism, is set down as an intellectual
virtue, so also should opinion be.

_On the contrary,_ The Philosopher (Ethic. vi, 1) reckons these three
alone as being intellectual virtues, viz. wisdom, science and
understanding.

_I answer that,_ As already stated (A. 1), the virtues of the
speculative intellect are those which perfect the speculative
intellect for the consideration of truth: for this is its good work.
Now a truth is subject to a twofold consideration--as known in
itself, and as known through another. What is known in itself, is as
a _principle,_ and is at once understood by the intellect: wherefore
the habit that perfects the intellect for the consideration of such
truth is called _understanding,_ which is the habit of principles.

On the other hand, a truth which is known through another, is
understood by the intellect, not at once, but by means of the
reason's inquiry, and is as a _term._ This may happen in two ways:
first, so that it is the last in some particular genus; secondly, so
that it is the ultimate term of all human knowledge. And, since
"things that are knowable last from our standpoint, are knowable
first and chiefly in their nature" (Phys. i, text. 2, 3); hence that
which is last with respect to all human knowledge, is that which is
knowable first and chiefly in its nature. And about these is
_wisdom,_ which considers the highest causes, as stated in _Metaph._
i, 1, 2. Wherefore it rightly judges all things and sets them in
order, because there can be no perfect and universal judgment that is
not based on the first causes. But in regard to that which is last in
this or th