The Complete Aristotle (eng.)

all privation is a privation
of some natural attribute, so that the addition of the word
‘natural’ is superfluous: it would have been enough to say
‘privation of heat’, for the word ‘privation’ shows of itself that
the heat meant is natural heat.
    Again, see if a universal have been mentioned and then a
particular case of it be added as well, e.g. ‘Equity is a remission
of what is expedient and just’; for what is just is a branch of
what is expedient and is therefore included in the latter term: its
mention is therefore redundant, an addition of the particular after
the universal has been already stated. So also, if he defines
‘medicine’ as ‘knowledge of what makes for health in animals and
men’, or ‘the law’ as ‘the image of what is by nature noble and
just’; for what is just is a branch of what is noble, so that he
says the same thing more than once.
<
    div id="section53" class="section" title="4">
4
    Whether, then, a man defines a thing correctly or incorrectly
you should proceed to examine on these and similar lines. But
whether he has mentioned and defined its essence or no, should be
examined as follows: First of all, see if he has failed to make the
definition through terms that are prior and more intelligible. For
the reason why the definition is rendered is to make known the term
stated, and we make things known by taking not any random terms,
but such as are prior and more intelligible, as is done in
demonstrations (for so it is with all teaching and learning);
accordingly, it is clear that a man who does not define through
terms of this kind has not defined at all. Otherwise, there will be
more than one definition of the same thing: for clearly he who
defines through terms that are prior and more intelligible has also
framed a definition, and a better one, so that both would then be
definitions of the same object. This sort of view, however, does
not generally find acceptance: for of each real object the essence
is single: if, then, there are to be a number of definitions of the
same thing, the essence of the object will be the same as it is
represented to be in each of the definitions, and these
representations are not the same, inasmuch as the definitions are
different. Clearly, then, any one who has not defined a thing
through terms that are prior and more intelligible has not defined
it at all.
    The statement that a definition has not been made through more
intelligible terms may be understood in two senses, either
supposing that its terms are absolutely less intelligible, or
supposing that they are less intelligible to us: for either sense
is possible. Thus absolutely the prior is more intelligible than
the posterior, a point, for instance, than a line, a line than a
plane, and a plane than a solid; just as also a unit is more
intelligible than a number; for it is the prius and starting-point
of all number. Likewise, also, a letter is more intelligible than a
syllable. Whereas to us it sometimes happens that the converse is
the case: for the solid falls under perception most of all-more
than a plane-and a plane more than a line, and a line more than a
point; for most people learn things like the former earlier than
the latter; for any ordinary intelligence can grasp them, whereas
the others require an exact and exceptional understanding.
    Absolutely, then, it is better to try to make what is posterior
known through what is prior, inasmuch as such a way of procedure is
more scientific. Of course, in dealing with persons who cannot
recognize things through terms of that kind, it may perhaps be
necessary to frame the expression through terms that are
intelligible to them. Among definitions of this kind are those of a
point, a line, and a plane, all of which explain the prior by the
posterior; for they say that a point is the limit of a line, a line
of a plane, a plane of a solid. One must, however, not fail to
observe that those who define in this way cannot show the essential
nature of the term they define, unless it so happens that the same
thing is more intelligible both to us and also absolutely, since a
correct definition must define a thing through its genus and its
differentiae, and these belong to the order of things which are
absolutely more intelligible than, and prior to, the species. For
annul the genus and differentia, and the species too is annulled,
so that these are prior to the species. They are also more
intelligible; for if the species be known, the