Metaphor of a bad mind

I am inclined to suspect, that all these several finders of truth are the very identical men, who are by others called the finders of gold. The method used in both these searches after truth and after gold, being, indeed, one and the same, viz. the searching, rummaging, and examining into a nasty place; indeed, in the former instances, into the nastiest of all places, A BAD MIND.
But though in this particular, and, perhaps, in their success, the truth-finder and the gold-finder may very properly be compared together; yet, in modesty, surely, there can be no comparison between the two: for who ever heard of a gold-finder that had the impudence or folloy to assert, from the ill-success of his search, that there was no such thing as gold in the world? Whereas the truth-finder, having raked out that jakes, his own mind, and being there capable of tracing no ray of divinity, nor any thing virtuous or good, or lovely or loving, very fairly, honestly, and logically, concludes, that no such things exist in the whole creation.

Henry Fielding, The History of Tom Jones, A Foundling (1749), Book VI, Chapter One, Of Love.

Note

A gold-finder was one who emptied privies.

De Nihilo

As Nothing is not Something, so every thing which is not Something, is Nothing; and wherever Something is not, Nothing is (...) For instance; when a Bladder is full of Wind, it is full of Something; but when that is let out, we aptly say, there is Nothing in it. The same may be as justly asserted of a Man as of a Bladder. However well he may be bedaubed with Lace, or with Title, yet if he have not Something in him, we may predicate the same of him as of an empty Bladder. (...) Indeed some have imagined, that Knowledge, with the adjective human placed before it, is another word for Nothing. And one of the wisest Men in the world declared, he knew Nothing. But without carrying it so far, this I believe may be allowed: it is at least possible for a Man to know Nothing. And whoever hath read over many Works of our ingenious Moderns, with proper Attention and Emolument, will, I believe, confess, that if he understands them right, he understands Nothing.

Henry Fielding, "An Essay on Nothing", Miscellanies, Vol. 3 (London, 1743)