The known is finite, the unknown infinite

From The Life and Letters of Charles Darwin by Francis Darwin (Appleton, 1904), vol. 1., On the Reception of the Origin of Species chapter by Thomas Huxley.

The known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land, to add something to the extent and the solidity of our possessions.