Whether we take these characters then, or such minor ones as those which are derivable from the proportional length of the spines in the cervical ver… - Thomas Henry Huxley

The extent of the region of the uncertain, the number of the problems the investigation of which ends in a verdict of not proven, will vary according to the knowledge and the intellectual habits of the individual agnostic. I do not very much care to speak of anything as unknowable. What I am sure about is that there are many topics about which I know nothing, and which, so far as I can see, are out of reach of my faculties. But whether these things are knowable by any one else is exactly one of those matters which is beyond my knowledge, though I may have a tolerably strong opinion as to the probabilities of the case.

The great end of life is not knowledge but action. Try to learn something about everything and everything about something.

The facts of variability, of the struggle for existence, of adaptation to conditions, were notorious enough; but none of us had suspected that the road to the heart of the species problem lay through them, until Darwin and Wallace dispelled the darkness.