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any one describes what betokens and what produces health as 'related
commensurably to health', we must not desist but go on to examine in
what sense he has used the term 'commensurably' in each case, e.g. if
in the latter case it means that 'it is of the right amount to produce
health', whereas in the for it means that 'it is such as to betoken
what kind of state prevails'.
Moreover, see if the terms cannot be compared as 'more or less' or as
'in like manner', as is the case (e.g.) with a 'clear' (lit. white)
sound and a 'clear' garment, and a 'sharp' flavour and a 'sharp' note.
For neither are these things said to be clear or sharp 'in a like
degree', nor yet is the one said to be clearer or sharper than the
other. 'Clear', then, and 'sharp' are ambiguous. For synonyms are
always comparable; for they will always be used either in like manner,
or else in a greater degree in one case.
Now since of genera that are different without being subaltern the
differentiae also are different in kind, e.g. those of 'animal' and
'knowledge' (for the differentiae of these are different), look and
see if the meanings comprised under the same term are differentiae of
genera that are different without being subaltern, as e.g. 'sharp' is
of a 'note' and a 'solid'. For being 'sharp' differentiates note from
note, and likewise also one solid from another. 'Sharp', then, is an
ambiguous term: for it forms differentiae of genera that are different
without being subaltern.
Again, see if the actual meanings included under the same term
themselves have different differentiae, e.g. 'colour' in bodies and
'colour' in tunes: for the differentiae of 'colour' in bodies are
'sight-piercing' and 'sight compressing', whereas 'colour' in melodies
has not the same differentiae. Colour, then, is an ambiguous term; for
things that are the same have the same differentiae.
Moreover, since the species is never the differentia of anything, look
and see if one of the meanings included under the same term be a
species and another a differentia, as (e.g.) clear' (lit. white) as
applied to a body is a species of colour, whereas in the case of a
note it is a differentia; for one note is differentiated from another
by being 'clear'.
Part 16
The presence, then, of a number of meanings in a term may be
investigated by these and like means. The differences which things
present to each other should be examined within the same genera, e.g.
'Wherein does justice differ from courage, and wisdom from
temperance?'-for all these belong to the same genus; and also from one
genus to another, provided they be not very much too far apart, e.g.
'Wherein does sensation differ from knowledge?: for in the case of
genera that are very far apart, the differences are entirely obvious.
Part 17
Likeness should be studied, first, in the case of things belonging to
different genera, the formulae being 'A:B = C:D' (e.g. as knowledge
stands to the object of knowledge, so is sensation related to the
object of sensation), and 'As A is in B, so is C in D' (e.g. as sight
is in the eye, so is reason in the soul, and as is a calm in the sea,
so is windlessness in the air). Practice is more especially needed in
regard to terms that are far apart; for in the case of the rest, we
shall be more easily able to see in one glance the points of likeness.
We should also look at things which belong to the same genus, to see
if any identical attribute belongs to them all, e.g. to a man and a
horse and a dog; for in so far as they have any identical attribute,
in so far they are alike.
Part 18
It is useful to have examined the number of meanings of a term both
for clearness' sake (for a man is more likely to know what it is he
asserts, if it bas been made clear to him how many meanings it may
have), and also with a view to ensuring that our reasonings shall be
in accordance with the actual facts and not addressed merely to the
term used. For as long as it is not clear in how many senses a term is