The Complete Aristotle (eng.)

for this
both involves no reasoning and is something that is quick in its
operation, while men deliberate a long time, and they say that one
should carry out quickly the conclusions of one’s deliberation, but
should deliberate slowly. Again, readiness of mind is different
from excellence in deliberation; it is a sort of skill in
conjecture. Nor again is excellence in deliberation opinion of any
sort. But since the man who deliberates badly makes a mistake,
while he who deliberates well does so correctly, excellence in
deliberation is clearly a kind of correctness, but neither of
knowledge nor of opinion; for there is no such thing as correctness
of knowledge (since there is no such thing as error of knowledge),
and correctness of opinion is truth; and at the same time
everything that is an object of opinion is already determined. But
again excellence in deliberation involves reasoning. The remaining
alternative, then, is that it is correctness of thinking; for this
is not yet assertion, since, while even opinion is not inquiry but
has reached the stage of assertion, the man who is deliberating,
whether he does so well or ill, is searching for something and
calculating.
    But excellence in deliberation is a certain correctness of
deliberation; hence we must first inquire what deliberation is and
what it is about. And, there being more than one kind of
correctness, plainly excellence in deliberation is not any and
every kind; for (1) the incontinent man and the bad man, if he is
clever, will reach as a result of his calculation what he sets
before himself, so that he will have deliberated correctly, but he
will have got for himself a great evil. Now to have deliberated
well is thought to be a good thing; for it is this kind of
correctness of deliberation that is excellence in deliberation,
viz. that which tends to attain what is good. But (2) it is
possible to attain even good by a false syllogism, and to attain
what one ought to do but not by the right means, the middle term
being false; so that this too is not yet excellence in deliberation
this state in virtue of which one attains what one ought but not by
the right means. Again (3) it is possible to attain it by long
deliberation while another man attains it quickly. Therefore in the
former case we have not yet got excellence in deliberation, which
is rightness with regard to the expedient-rightness in respect both
of the end, the manner, and the time. (4) Further it is possible to
have deliberated well either in the unqualified sense or with
reference to a particular end. Excellence in deliberation in the
unqualified sense, then, is that which succeeds with reference to
what is the end in the unqualified sense, and excellence in
deliberation in a particular sense is that which succeeds
relatively to a particular end. If, then, it is characteristic of
men of practical wisdom to have deliberated well, excellence in
deliberation will be correctness with regard to what conduces to
the end of which practical wisdom is the true apprehension.
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10
    Understanding, also, and goodness of understanding, in virtue of
which men are said to be men of understanding or of good
understanding, are neither entirely the same as opinion or
scientific knowledge (for at that rate all men would have been men
of understanding), nor are they one of the particular sciences,
such as medicine, the science of things connected with health, or
geometry, the science of spatial magnitudes. For understanding is
neither about things that are always and are unchangeable, nor
about any and every one of the things that come into being, but
about things which may become subjects of questioning and
deliberation. Hence it is about the same objects as practical
wisdom; but understanding and practical wisdom are not the same.
For practical wisdom issues commands, since its end is what ought
to be done or not to be done; but understanding only judges.
(Understanding is identical with goodness of understanding, men of
understanding with men of good understanding.) Now understanding is
neither the having nor the acquiring of practical wisdom; but as
learning is called understanding when it means the exercise of the
faculty of knowledge, so ‘understanding’ is applicable to the
exercise of the faculty of opinion for the purpose of judging of
what some one else says about matters with which practical wisdom
is concerned-and of judging soundly; for ‘well’ and ‘soundly’