“We come late, if at all, to wine and philosophy; whiskey and action are easier.”

Preface xxx
Variant: When philosophy paints its grey on grey, then has a shape of life grown old. By philosophy's grey on grey it cannot be rejuvenated but only understood. The owl of Minerva spreads its wings only with the falling of the dusk.
As translated by T. M. Knox, (1952) <!-- p. 13 -->
Elements of the Philosophy of Right (1820/1821)
Context: Only one word more concerning the desire to teach the world what it ought to be. For such a purpose philosophy at least always comes too late. Philosophy, as the thought of the world, does not appear until reality has completed its formative process, and made itself ready. History thus corroborates the teaching of the conception that only in the maturity of reality does the ideal appear as counterpart to the real, apprehends the real world in its substance, and shapes it into an intellectual kingdom. When philosophy paints its grey in grey, one form of life has become old, and by means of grey it cannot be rejuvenated, but only known. The owl of Minerva takes its flight only when the shades of night are gathering.

A Drinking Song http://poetry.poetryx.com/poems/1399/
The Green Helmet and Other Poems (1910)

On the Death of Mr. William Harvey; reported in Bartlett's Familiar Quotations, 10th ed. (1919).

Source: Les Misérables

As quoted in Diogenes Laertius, The Lives and Opinions of Eminent Philosophers, Chapter "Life of Anacharsis", 1702 edition, John Nicholson, p. 55

Physics and Philiosophy in Oxford: a prosperous example of interdisciplinarity, in [Innovation and interdisciplinarity in the university, EDIPUCRS, 2007, 8-574-30677-0, 308 http://books.google.com/books?id=-OGr007TQ0AC&printsec=frontcover#PPA308,M1]