The aim of this work is to account for expressions like “Cantor’s diagonal proof is elegant” or “Euler identity is the most beautiful formula of mathematics”. This type of expressions is common among mathematicians; however, they may result in two kinds of puzzled reactions: first, the non mathematician may find the use of the word ‘beautiful’ strange in this context. Second, the mathematician may try to reinterpret mathematical beauty in terms of the principles and precepts of mathematics itself. I present (...) an account of mathematical beauty that offers a way to avoid these puzzled reactions: mathematical beauty is just a type of “normal” beauty and no reinterpretation is necessary. To support this claim, I devise an aesthetic theory -by using insights and findings from experimental psychology, neurology, philosophical and psychological theories of emotion in art, philosophy of music and philosophy of science- that shows that aesthetic judgments in mathematics are genuine aesthetic judgments. (shrink)