We find in the history of ideas mutations which do not seem to correspond to any obvious need, and at first sight appear as mere playful whimsies — such as Apollonius' work on conic sections, or the non-Euclidean geometries, whose practical value became apparent only later.

as quoted by Michael Grossman in the The First Nonlinear System of Differential and Integral Calculus (1979). - The Sleepwalkers: A History of Man's Changing Vision of the Universe (1959)