The most important pun in the English language - Christopher Ricks.

Some words on truth

As with  sense, so with lie  the importance of a pun must be in the first place a matter of the enduring and central matters which it encompasses. Lies are important irrespective of any pun that may visit them. For one thing, the telling of the truth is necessary to those social and cultural agreements without which there cannot be a society or a culture. Even the devils know this, for as Sir Thomas Browne said ' so also in \moral verities, although they decieve us,  they lie not unto each other; as well understanding that all community is continued by Truth, and that of Hell cannot exist without it.'  For another thing, telling the truth is a necessary condition for the existence of a language at all. Which is why in the language - indeed, in most of all languages, one may guess - there is no truth verb that is the counterpart to the verb to lie. (And there are, from similar causes or with similar effects, no puns on true and truth that amount to anything.) You cannot truth , a fact which both makes the telling of a truth a less glib matter than lying ('the truth, the whole truth, and nothing but the truth'), and also brings out the speaking has to be posited on a presumption of the speaking of the truth. Even if it were not accepted that words about words all have a special force, though not necessarily a grater force than other words ( for this claim might be merely a literary critic's professional predilection), it is nevertheless the case that lie  has the special potency of immediate paradoxiical properties, since it strikes at the roots of language and may strike, self-incrimiinattingly, at itself. The importance of lying therefore ranges from all those daily falsehoods in the orinary world to such absract but intense considerations  of language, society, and philosophy. In 1970 there was published a book wholly devotted to the paradox of the liar.
Yet the importance of the phenomenem oflying is necessary but not sufficient condition of any claimed importance for the pun on lie and lying. Then there are the linguistic pressures on the word lie  which themselves make the word a creator of pressure. There is, first, a depoulation around lie which gives it the potency of salience. For instance, lie calls up no manifest etymolology for us; as ashort and simple Old English word, it seems - as does the word truth - to be a root concept behind or below which we cannot penetrate. ( The contrast would be with the words veracity  and mendacity  which sends our toughts abroad, in both senses.) Next there is the fact that there are no profound or memorable proverbs about lies or truth, so that the words themselves have to muster all the energy of the phenomena. A comparable depopulation, lending prominence and salience to lie and truth, is that by which a great many lie and truth terms have fallen out of the language, as if by some evolutionary concentration upon the survival of the fittest words. Middle English gab, to lie , survives only in its weakened child, gabble; leasing has gone as has the plural lyings;  the adjective lie ( from Old English  lyze, lying); various tansistive and quasi-transistive uses of to lie (OED 3 and 4 ); and 'to give the lieto' ( accuse of lyiing). You can no longer 'make a lie', you can only tell it; you can now lie only about, not - as you can only tell it; you can now lie only about, not - as you once could - of, on, or upon (OED 1b).
Again, there is the salience given by the marked absence of synonyms for lie; all we have is either ephemeral or infantile slang (bounce, crammer, whopper, fib - to cite Roget's Thesarus ) or eupehemisms: falsehood and untruth, neither of which strictly means lie and both of which therefore can on occasions have the special offence of a euphemism.
.... The final linguistic consideration is one of the many asymmetries between lie and truth,  one which lends to lie ( and to its pun) a range of suggestions which are denied to or disdained by truth. This is the fact that rhymes for truth are few, and only one of them * has much potentiality for discovering or urging insights...
This marked paucity of suggestive rhyming for truth, which lends it a lonely dignity and integrity, contrasts sharply with the manifest and manifold rhymes which crowd upon or from lie: fly ( with its altruism or cowardice), die ( with its moment of truth and its horizantality), I and my ( with their sincerity or insincerity), eye ( with its honesty or shiftiness), and so on.
... It is Shakespear's work which provides the transition from those linguistic considerations which give salience to the  lie/lie pun, to the more largely human considerations which give importance to it. For there is a prima facie likelihood that a pun which is so ubiquiously necessary to the greatest writer inthe language is a very important pun. Shakespear, who needs and wants the words lie, lies, and lying  hundreds of times in his work, has only three times thepunless form lied. We should ask ourselves whether the fretfulness or impatience which we sometimes feel with these puns is to Shakespeare's siscredit or to ours- have we lost, or bebome blinded to, the important considerations that presumably seemed to Shakespeare to raise above triviality such an insistence as this?

                                That, Lye, shall lieso heavy on my Sword,
                                That it shall render Vengeance, and Revenge,
                                Till thou the Lye-giver, and that Lye, do Lye
                                In earth as quiet, as thy Father's Scull.
                                                                         ( Richard 11 !V.i)
... The importance of the llie/lie is that it concentates an exraordinary wide-ranging and profound network of truth testing situations and postures. It brings mendacity up against those situations and postures which constitute thegreat moments or endurances of truth: the child-bed, the love-bed, the bed of sleep and dreams, the sick-bed, the death-bed, the grave....And even perhaps the modern secular counterpart to the confessional's kneeling: the psychiatrist's couch. It conentrates this network, or rather concentrated it, since historical and cultural circumstances are now disintegrating it.             

* The word 'youth'.

Christopher Ricks
Reprinted from:-
'Lies, in The Force of Poetry,
Oxford University Press, 1984.