In all discussion of metaphor it must be borne in mind that some
metaphors are living, i.e. are offered and accepted with a
consciousness of their nature as substitutes for their literal
equivalents, while others are dead, i.e. have been so often used that
speaker and hearer have ceased to be aware that the words are not
literal: but the line of distinction between the live and the dead is
a shifting one, the dead being sometimes liable, under the stimulus of
an affinity or a repulsion, to galvanic stirrings indistinguishable
from life. Thus, in _The men were sifting meal_ we have a literal use
of _sift_; in _Satan hath desired to have you, that he may sift you as
wheat_, 'sift' is a live metaphor; in _the sifting of evidence_, the
metaphor is so familiar that it is about equal chances whether
_sifting_ or _examination_ will be used, and a sieve is not present to
the thought--unless, indeed, some one conjures it up by saying _All
the evidence must first be sifted with acid tests_, or _with the
microscope_; under such a stimulus our metaphor turns out to have been
not dead, but dormant. The other word, _examine_, will do well enough
as an example of the real stone-dead metaphor; the Latin _examino_,
being from _examen_ the tongue of a balance, meant originally to
weigh; but, though weighing is not done with acid tests or microscopes
any more than sifting, _examine_ gives no convulsive twitchings, like
_sift_, at finding itself in their company; _examine_, then, is dead
metaphor, and _sift_ only half dead, or three-quarters.
2. Some pitfalls. A, Unsustained Metaphor; B, Overdone Metaphor; C,
Spoilt Metaphor; D, Battles of the Dead; E, Mixed Metaphor.