The world is like a change-office, without increase or decrease in its initial stock. We always stand in the middle of an equation, past equalling future. It is for the biologist to correct this partial view, for to him the possible that grows out of the past is new and in some measure unpredictable.

The System of Animate Nature: The Gifford Lectures Delivered in the, University of St. Andrews in the Years 1915 and 1916 Volume 2, Lecture XI (p. 358), Henry Holt & Co. 1920