"I am afraid I am not in the flight for “aerial navigation”. I was greatly interested in your work with kites; but I have not the smallest molecule of faith in aerial navigation other than ballooning or of expectation of good results from any of the trials we hear of. So you will understand that I would not care to be a member of the aëronautical Society."

"Symmetrical equations are good in their place, but 'vector' is a useless survival, or offshoot from quaternions, and has never been of the slightest use to any creature."

"Mathematics is the only true metaphysics."

"Do not imagine that mathematics is hard and crabbed, and repulsive to common sense. It is merely the etherealization of common sense."