Erdös, Paul 
A Mathematician is a machine for turning coffee into theorems. 

Besicovitch, A.S. 
A mathematician's reputation rests on the number of bad proofs he has given. 

Carmichael, R. D. 
A thing is obvious mathematically after you see it. 

De Sua, F. (1956) 
Suppose we loosely define a religion as any discipline whose foundations 
rest on an element of faith, irrespective of any element of reason which may be present. 
Quantum mechanics for example would be a religion under this definition. 
But mathematics would hold the unique position of being the only branch of theology 
possessing a rigorous demonstration of the fact that it should be so classified. 

Eddington, Sir Arthur (1882-1944) 
We used to think that if we knew one, we knew two, because one and one are two. 
We are finding that we must learn a great deal more about `and'. 

Egrafov, M. 
If you ask mathematicians what they do, yo always get the same answer. 
They think. 
They think about difficult and unusual problems. 
They do not think about ordinary problems: 
they just write down the answers. 

Einstein, Albert (1879-1955) 
Common sense is the collection of prejudices acquired by age eighteen. 

Gauss, Karl Friedrich (1777-1855) 
I have had my results for a long time: 
but I do not yet know how I am to arrive at them. 

Gordon, P 
This is not mathematics, it is theology. 

Hadamard, Jacques 
The shortest path between two truths in the real domain passes through the complex domain. 

Halmos, Paul R. 
I remember one occasion when I tried to add a little seasoning to a review, but I wasn't allowed to. 
The paper was by Dorothy Maharam, and it was a perfectly sound contribution to abstract measure theory. 
The domains of the underlying measures were not sets but elements of more general Boolean algebras, 
and their range consisted not of positive numbers but of certain abstract equivalence classes. 
My proposed first sentence was: "The author discusses valueless measures in pointless spaces." 

Hofstadter, Douglas R. (1945 - ) 
Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law. 

Kelley, John 
A topologist is one who doesn't know the difference between a doughnut and a coffee cup. 

Luther, Martin (1483-1546) 
Medicine makes people ill, mathematics make them sad and theology makes them sinful. 

Poisson, Siméon (1781-1840) 
Life is good for only two things, discovering mathematics and teaching mathematics. 

Polyá, George (1887, 1985) 
Mathematics consists of proving the most obvious thing in the least obvious way. 

Polyá, George (1887, 1985) 
The traditional mathematics professor of the popular legend is absentminded. 
He usually appears in public with a lost umbrella in each hand. 
He prefers to face the blackboard and to turn his back to the class. 
He writes a, he says b, he means c; but it should be d. 
Some of his sayings are handed down from generation to generation:
"In order to solve this differential equation you look at it till a solution occurs to you." 
"This principle is so perfectly general that no particular application of it is possible." 
"Geometry is the science of correct reasoning on incorrect figures." 
"My method to overcome a difficulty is to go round it." 
"What is the difference between method and device? A method is a device which you used twice."