The work of science is to substitute facts for appearances, and demonstrations for impressions. John Ruskin
What is a wife and what is a harlot? What is a church and what is a theatre? are they two and not one? Can they exist separate? Are not religion and politics the same thing? Brotherhood is religion. O demonstrations of reason dividing families in cruelty and pride! William Blake
All sports are time control demonstrations. Buckminster Fuller
A sane mind should not be guilty of a logical fallacy, yet there are very fine minds incapable of following mathematical demonstrations. Henri Poincaré
Mathematics is of two kinds, Rigorous and Physical. The former is Narrow: the latter Bold and Broad. To have to stop to formulate rigorous demonstrations would put a stop to most physico-mathematical inquiries. Am I to refuse to eat because I do not fully understand the mechanism of digestion? Oliver Heaviside
I don't belong to any club or group. I don't fish, cook, dance, endorse books, sign books, co-sign declarations, eat oysters, get drunk, go to church, go to analysts, or take part in demonstrations. Vladimir Nabokov