uch epithets may be applicable to objects on account of
different qualities: _good_ is not predicated on the same ground of a
man and of a horse.

(7) In defining any word, it is desirable to bear in mind its
derivation, and to preserve the connection of meaning with its origin;
unless there are preponderant reasons for diverting it, grounded on our
need of the word to express a certain sense, and the greater difficulty
of finding any other word for the same purpose. It is better to lean to
the classical than to the vulgar sense of 'indifferent,' 'impertinent,'
'aggravating,' 'phenomenal.'

(8) Rigorous definition should not be attempted where the subject does
not admit of it. Some kinds of things are so complex in their qualities,
and each quality may manifest itself in so many degrees without ever
admitting of exact measurement, that we have no means of marking them
off precisely from other things nearly allied, similarly complex and
similarly variable. If so we cannot precisely define their names.
Imagination and fancy are of this nature, civilisation and barbarism,
poetry and other kinds of literary expression. As to poetry, some think
it only exists in metre, but hardly maintain that the metre must be
strictly regular: if not, how much irregularity of rhythm is admissible?
Others regard a certain mood of impassioned imagination as the essence
of poetry; but they have never told us how great intensity of this mood
is requisite. We also hear that poetry is of such a nature that the
enjoyment of it is an end in itself; but as it is not maintained that
poetry must be wholly impersuasive or uninstructive, there seems to be
no means of deciding what amount or prominence of persuasion or
instruction would transfer the work to the region of oratory or science.
Such cases make the method of defining by the aid of a type really
useful: the difficulty can hardly be got over without pointing to
typical examples of each meaning, and admitting that there may be many
divergences and unclassifiable instances on the border between allied
meanings.

Sec. 5. As science began from common knowledge, the terms of the common
vocabulary have often been adopted into the sciences, and many are still
found there: such as weight, mass, work, attraction, repulsion,
diffusion, reflection, absorption, base, salt, and so forth. In the more
exact sciences, the vague popular associations with such words are
hardly an inconvenience: since those a