“The principles on which the philosopher uses language are those of poetry, but what he writes is not poetry but prose. From the point of view of literary form, this means that whereas the poet yields himself to every suggestion that his language makes, and so produces word-patterns whose beauty is a sufficient reason for their existence, the philosopher’s word-patterns are constructed only to reveal the thought which they express, and are valuable not in themselves but as means to that end. The prose writers 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 jeweler 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”.

Collingwood, R. G. “Philosophy as a Branch of Literature.” In An Essay on Philosophical Method. Oxford: Oxford University Press, 1933.