Froth and scum
Aut insanit Homo, aut versus facit—
[The man is either raving or composing. Hor. Sat. 7. lib. 2.]
Composing and Raving must necessarily, we see, bear a resemblance. And for those Composers who deal in Systems, and airy Speculations, they have vulgarly pass’d for a sort of Prose-Poets. Their secret Practice and Habit has been as frequently noted:
Murmura cùm secum & rabiosa silentia rodunt.
[They chew over mumbles with themselves and rabid silences. Pers. Sat. 3.]
Both these sorts are happily indulg’d in this Method of Evacuation. They are thought to act naturally, and in their proper way, when they assume these odd Manners. But of other Authors ’tis expected they shou’d be better bred. They are oblig’d to preserve a more conversible Habit; which is no small misfortune to ’em. For if their Meditation and Resvery be obstructed by the fear of a nonconforming Mein in Conversation, they may happen to be so much the worse Authors for being finer Gentlemen. Their Fervency of Imagination may possibly be as strong as either the Philosopher’s or the Poet’s. But being deny’d an equal Benefit of Discharge, and with-held from the wholesom manner of Relief in private; ’tis no wonder if they appear with so much Froth and Scum in publick.
’Tis observable, that the Writers of Memoirs and Essays are chiefly subject to this frothy Distemper. Nor can it be doubted that this is the true Reason why these Gentlemen entertain the World so lavishly with what relates to themselves. For having had no opportunity of privately conversing with themselves, or exercising their own Genius, so as to make Acquaintance with it, or prove its Strength; they immediately fall to work in a wrong place, and exhibit on the Stage of the World that Practice, which they shou’d have kept to themselves; if they design’d that either they, or the World, shou’d be the better for their Moralitys. Who indeed can endure to hear an Empirick talk of his own Constitution, how he governs and manages it, what Diet agrees best with it, and what his Practice is with himself? The Proverb, no doubt, is very just, Physician cure thy-self. Yet methinks one shou’d have but an ill time, to be present at these bodily Operations. Nor is the Reader in truth any better entertain’d, when he is oblig’d to assist at the experimental Discussions of his practising Author, who all the while is in reality doing no better, than taking his Physick in publick.
Anthony Ashley Cooper, Earl of Shaftesbury, "Soliloquy: or, Advice to an Author," Characteristicks of Men, Manners, Opinions, Times, vol. 1 
December 13, 2009 1:16 PM