It has often been said that if individual experience could not create geometry the same is not true of ancestral experience. But what does that mean? Is it meant that we could not experimentally demonstrate Euclid's postulate, but that our ancestors have been able to do it? Not in the least. It is meant that by natural selection our mind has _adapted_ itself to the conditions of the external world, that it has adopted the geometry _most advantageous_ to the species: or in other words _the most convenient_. This is entirely in conformity with our conclusions; geometry is not true, it is advantageous.
ANCESTRAL EXPERIENCE
From The Foundations of Science by Henri Poincaré.
