Date: 1800

"They grow by certain laws, like the tree's fruit-- / No juggling chance can metamorphose them. / Have I the human kernel first examined? / Then I know, too, the future will and action."

— Schiller, Friedrich (1759-1805)

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: September, 1838

"The tree of my mind of its leaves is stripped, my witticisms too fine are clipped, the kernel out of the shell has been nipped."

— Engels, Friedrich (1820-1895)