The Complete Aristotle (eng.)

useful be more
desirable, then also what is useful is desirable. Likewise, also,
in the case of other things which admit of comparisons of that
kind. For in some cases in the very course of comparing the things
together we at once assert also that each of them, or the one of
them, is desirable, e.g. whenever we call the one good ‘by nature’
and the other ‘not by nature’: for dearly what is good by nature is
desirable.
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5
    The commonplace rules relating to comparative degrees and
amounts ought to be taken in the most general possible form: for
when so taken they are likely to be useful in a larger number of
instances. It is possible to render some of the actual rules given
above more universal by a slight alteration of the expression, e.g.
that what by nature exhibits such and such a quality exhibits that
quality in a greater degree than what exhibits it not by nature.
Also, if one thing does, and another does not, impart such and such
a quality to that which possesses it, or to which it belongs, then
whichever does impart it is of that quality in greater degree than
the one which does not impart it; and if both impart it, then that
one exhibits it in a greater degree which imparts it in a greater
degree.
    Moreover, if in any character one thing exceeds and another
falls short of the same standard; also, if the one exceeds
something which exceeds a given standard, while the other does not
reach that standard, then clearly the first-named thing exhibits
that character in a greater degree. Moreover, you should judge by
means of addition, and see if A when added to the same thing as B
imparts to the whole such and such a character in a more marked
degree than B, or if, when added to a thing which exhibits that
character in a less degree, it imparts that character to the whole
in a greater degree. Likewise, also, you may judge by means of
subtraction: for a thing upon whose subtraction the remainder
exhibits such and such a character in a less degree, itself
exhibits that character in a greater degree. Also, things exhibit
such and such a character in a greater degree if more free from
admixture with their contraries; e.g. that is whiter which is more
free from admixture with black. Moreover, apart from the rules
given above, that has such and such a character in greater degree
which admits in a greater degree of the definition proper to the
given character; e.g. if the definition of ‘white’ be ‘a colour
which pierces the vision’, then that is whiter which is in a
greater degree a colour that pierces the vision.
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6
    If the question be put in a particular and not in a universal
form, in the first place the universal constructive or destructive
commonplace rules that have been given may all be brought into use.
For in demolishing or establishing a thing universally we also show
it in particular: for if it be true of all, it is true also of
some, and if untrue of all, it is untrue of some. Especially handy
and of general application are the commonplace rules that are drawn
from the opposites and co-ordinates and inflexions of a thing: for
public opinion grants alike the claim that if all pleasure be good,
then also all pain is evil, and the claim that if some pleasure be
good, then also some pain is evil. Moreover, if some form of
sensation be not a capacity, then also some form of failure of
sensation is not a failure of capacity. Also, if the object of
conception is in some cases an object of knowledge, then also some
form of conceiving is knowledge. Again, if what is unjust be in
some cases good, then also what is just is in some cases evil; and
if what happens justly is in some cases evil, then also what
happens unjustly is in some cases good. Also, if what is pleasant
is in some cases objectionable, then pleasure is in some cases an
objectionable thing. On the same principle, also, if what is
pleasant is in some cases beneficial, then pleasure is in some
cases a beneficial thing. The case is the same also as regards the
things that destroy, and the processes of generation and
destruction. For if anything that destroys pleasure or knowledge be
in some cases good, then we may take it that pleasure or knowledge
is in some cases an evil thing. Likewise, also, if the destruction
of knowledge be in some cases a good thing or its production an
evil thing, then knowledge will be in some cases an evil thing;
e.g. if