Selected quotes from http://www.baylor.edu/math/index.php?id=88078:

It is nothing short of a miracle that modern methods of instruction have not yet entirely strangled the holy curiosity of inquiry. (Albert Einstein, 1879-1955)

God may not play dice with the universe, but something strange is going on with the prime numbers. (Paul Erdös, 1913-1996)

To those who do not know mathematics it is difficult to get across a real feeling as to the beauty, the deepest beauty, of nature … If you want to learn about nature, to appreciate nature, it is necessary to understand the language that she speaks in. (Richard Feynman, 1918-1988)

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. (Galileo Galilei, 1564-1642)

The total number of Dirichlet’s publications is not large: jewels are not weighed on a grocery scale. (C.F. Gauss, 1777-1885)

Reductio ad absurdum, which Euclid loved so much, is one of a mathematician’s finest weapons. It is a far finer gambit than any chess play: a chess player may offer the sacrifice of a pawn or even a piece, but a mathematician offers the game. (G.H. Hardy, 1877-1947)

If I were to awaken after having slept for a thousand years, my first question would be: Has the Riemann hypothesis been proven? (David Hilbert, 1862-1953)

God ever arithmetizes. (Carl Jacobi, 1804-1851) *(No idea what this one means – any guesses?)*

I read in the proof sheets of Hardy on Ramanujan: “As someone said, each of the positive integers was one of his personal friends.” My reaction was, “I wonder who said that; I wish I had.” In the next proof-sheets I read (what now stands), “It was Littlewood who said…” (J.E. Littlewood, 1885-1977)

What we know is not much. What we do not know is immense. (Allegedly the last words of Pierre-Simon Laplace, 1749-1827)

In the absence of any other proof, the thumb alone would convince me of God’s existence. (Isaac Newton, 1643-1727)

[On quantum mechanics] I don’t like it, and I’m sorry I ever had anything to do with it. (Erwin Schrödinger, 1887-1961)

By and large it is uniformly true that in mathematics there is a time lapse between a mathematical discovery and the moment it becomes useful; and that this lapse can be anything from 30 to 100 years, in some cases even more; and that the whole system seems to function without any direction, without any reference to usefulness, and without any desire to do things which are useful. (John von Neumann, 1903-1957) *Conflicts between my pure math and engineering sides…*

My work has always tried to unite the true with the beautiful and when I had to choose one or the other, I usually chose the beautiful. (Hermann Weyl, 1885-1955)