A question by Tony Jackson on the Narrative-L, and one possible answer I suggest:
—"How could we make the judgment that some metaphors are better than others unless we have somewhere in mind the notion that at some point in fact it's not just metaphor but some kind of actuality?"
If wit be well described by Pope, as being "that which has been often thought, but was never before so well expressed," they certainly never attained, nor ever sought it; for they endeavoured to be singular in their thoughts, and were careless of their diction. But Pope's account of wit is undoubtedly erroneous: he depresses it below its natural dignity, and reduces it from strength of thought to happiness of language.
If, by a more noble and more adequate conception, that be considered as wit which is, at once, natural and new, that which, though not obvious, is, upon its first production, acknowledged to be just; if it be that, which he that never found it, wonders how he missed; to wit of this kind the metaphysical poets have seldom risen. Their thoughts are often new, but seldom natural; they are not obvious, but neither are they just; and the reader, far from wondering that he missed them, wonders more frequently by what perverseness of industry they were ever found.
But wit, abstracted from its effects upon the hearer, may be more rigorously and philosophically considered as a kind of "discordia concors;" a combination of dissimilar images, or discovery of occult resemblances in things apparently unlike. Of wit, thus defined, they have more than enough. The most heterogeneous ideas are yoked by violence together; nature and art are ransacked for illustrations, comparisons, and allusions; their learning instructs, and their subtilty surprises; but the reader commonly thinks his improvement dearly bought, and, though he sometimes admires, is seldom pleased.
From Johnson's phrasing one might deduce that "wit is in the air"---that is, there is a communal pre-perception or readiness to acknowledge a perceived relationship as witty once it is established. That may involve some expenditure of semiotic energy, or intertextual power sometimes, on the part of the person who coins the metaphor, but part of the work was already done by the groundwork, or the situation, or a general perception of the way things are---now we know, now we see. It is a cognitive-psychological definition, /avant la lettre,/ of metaphor and wit as an instrument of cognition and communal awareness, of semiotic linking as a mode of social communication. Consciousness and cognition are big issues in Johnson's definition of true wit.