What is known in mathematics under the name of limit is everywhere present in life in the guise of some ideal, some excellence high-dwelling among the rocks, an "ever flying perfect" as Emerson calls it, unto which we may approximate nearer and nearer, but which we can never quite attain, save in aspiration.

The Human Worth of Rigorous Thinking: Essays and Addresses, Chapter III (p. 78), Columbia University Press. 1916