Our resident quote bleggar Fred Shapiro, editor of the Yale Book of Quotations, is back with another request. If you have a bleg of your own — it needn’t have anything to do with quotations — send it along here.
Photo: foundphotosljRecently, after a Wall Street Journal article named The Yale Book of Quotations as the second-most-essential reference book for home use, I initiated a discussion about the continuing vitality of print reference books.
Now a newly published volume provides me with a splendid example of how there is still a place for print reference in the world: the Princeton Companion to Mathematics, edited by Fields Medal winner Timothy Gowers and published by Princeton University Press. Because of the close link between economics and mathematics, many readers of the Freakonomics blog may find this book of interest.
The Princeton Companion to Mathematics combines a number of elements that may not be present in Wikipedia or other online sources: entries written by some of the world’s leading mathematicians, prose of real literary distinction, and beautiful design and production. All in all, a must-have reference in mathematical literacy.
For this week’s bleg, I invite suggestions of famous or compelling mathematical quotations.

Sex is the mathematical urge repressed. -Sigmund Freud
From Bernhard Riemann:
“If only I had the theorems! Then I should find the proofs easily enough.”
“In mathematics you don’t understand things. You just get used to them.” – John Von Neumann
Two more:
“Any good idea can be stated in fifty words or less.” – Stan Ulam
“In mathematics, you don’t understand things. You just get used to them.” – John von Neumann
“Anyone who cannot cope with mathematics is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe, and not make messes in the house.”
Robert A. Heinlein (The Notebooks of Lazarus Long)
There are 10 kinds of people – those who understand binary notation, and those who don’t.
“Math is built with facts as a house is built with bricks, but a collection of facts cannot be called mathematics anymore than a pile of bricks can be called a house.” ~Poincare
“Math is the second best thing.” ~John Benson
“In mathematics you don’t understand things. You just get used to them.”
Johann von Neumann