then let fall
     Your horrible pleasure; here I stand, your slave,
     A poor, infirm, weak, and despised old man: 
     But yet I call you servile ministers,
     That have with two pernicious daughters join’d
     Your high engender’d battles ’gainst a head
     So old and white as this.  O!  O! ’tis foul!

Shakespeare, long before this, in the Midsummer Night’s Dream, had noticed the resemblance between the lunatic, the lover, and the poet; and the partial truth that genius is allied to insanity was quite familiar to him.  But he presents here the supplementary half-truth that insanity is allied to genius.

He does not, however, put into the mouth of the insane Lear any such sublime passages as those just quoted.  Lear’s insanity, which destroys the coherence, also reduces the poetry of his imagination.  What it stimulates is that power of moral perception and reflection which had already been quickened by his sufferings.  This, however partial and however disconnectedly used, first appears, quite soon after the insanity has declared itself, in the idea that the naked beggar represents truth and reality, in contrast with those conventions, flatteries, and corruptions of the great world, by which Lear has so long been deceived and will never be deceived again: 

Is man no more than this?  Consider him well.  Thou owest the worm no silk, the beast no hide, the sheep no wool, the cat no perfume.  Ha! here’s three on’s are sophisticated:  thou art the thing itself.

Lear regards the beggar therefore with reverence and delight, as a person who is in the secret of things, and he longs to question him about their causes.  It is this same strain of thought which much later (IV. vi.), gaining far greater force, though the insanity has otherwise advanced, issues in those famous Timon-like speeches which make us realise the original strength of the old King’s mind.  And when this strain, on his recovery, unites with the streams of repentance and love, it produces that serene renunciation of the world, with its power and glory and resentments and revenges, which is expressed in the speech (V. iii.): 

     No, no, no, no!  Come, let’s away to prison: 
     We two alone will sing like birds i’ the cage: 
     When thou dost ask me blessing, I’ll kneel down,
     And ask of thee forgiveness:  so we’ll live,
     And pray, and sing, and tell old tales, and laugh
     At gilded butterflies, and hear poor rogues
     Talk of court news; and we’ll talk with them too,
     Who loses, and who wins; who’s in, who’s out;
     And take upon’s the mystery of things,
     As if we were God’s spies:  and we’ll wear out,
     In a wall’d prison, packs and sets of great ones,
     That ebb and flow by the moon.

This is that renunciation which is at the same time a sacrifice offered to the gods, and on which the gods themselves throw incense; and, it may be, it would never have been offered but for the knowledge that came to Lear in his madness.