Poincaré, Jules Henri. 1854-1912. French mathematician and physicist.

A sane mind should not be guilty of a logical fallacy, yet there are very fine minds incapable of following mathematical demonstrations.



Geometry is not true, it is advantageous.



...by natural selection our mind has adapted itself to the conditions of the external world. It has adopted the geometry most advantageous to the species or, in other words, the most convenient. Geometry is not true, it is advantageous.
Science and Method.