As we go catching and catching at this or that corner of knowledge, now getting a foresight of generous possibilities, now chilled with a glimpse of prudence, we may compare the headlong course of our years to a swift torrent in which a man is carried away; now he is dashed against a boulder, now he grapples for a moment to a trailing spray; at the end, he is hurled out and overwhelmed in a dark and bottomless ocean. We have no more than glimpses and touches; we are torn away from our theories; we are spun round and round and shown this or the other view of life, until only fools or knaves can hold to their opinions.

Robert Louis Stevenson (1850–1894) Scottish essayist, novelist, poet

Essay (1878-03), “Crabbed Age and Youth,” Cornhill Magazine, Vol. 37
    (Source)

Collected in Virginibus Puerisque and Other Papers, ch. 2 (1881).