Date: 1830

"To grasp intelligence as this night-like mine or pit in which is stored a world of infinitely many images and representations, yet without being in consciousness, is from the one point of view the universal postulate which bids us treat the notion as concrete, in the way we treat, for example, t...

— Hegel, G. W. F. (1770-1831)

Date: 1902

"If it were otherwise, no one could even set down on paper a closely reasoned argument, for the attention would be skipping like a stone hurrying down a sharp incline, or it would be moving hither and thither like a helpless shuttlecock at the mercy of eager players."

— Spiller, Gustav (1864-1940)

Date: 2006

"When there is no longer any wobble, then the mind is like an unwavering rock, more immovable than a mountain and harder than a diamond."

— Ajahn Brahm [born Peter Betts] (August 7, 1951)

Date: 2018

"Get in the mind shaft."

— White, Jack [John Anthony] (b. July 9, 1975)