" The prose-writer's art is an art that must conceal itself, and produce not a jewel that is looked at for its own beauty but a crystal in whose depths the thought can be seen without distortion or confusion ; and the philosophical writer in especial follows the trade not of a jeweller but of a lens-grinder. He must never use metaphors or imagery in such a way that they attract to themselves the attention due to his thought ;
if he does that he is writing not prose, but, whether well or ill, poetry; but he must avoid this not by rejecting all use of metaphors and imagery, but by using them, poetic things themselves, in the domestication of prose : using them just so far as to reveal thought, and no farther. "

― R.G. Collingwood , An Essay on Philosophical Method