books.google.com - The twentieth century has witnessed an unprecedented 'crisis in the foundations of mathematics', featuring a world-famous paradox (Russell's Paradox), a challenge to 'classical' mathematics from a world-famous mathematician (the 'mathematical intuitionism' of Brouwer), a new foundational school (Hilbert's...http://books.google.com/books/about/Philosophy_of_Mathematics.html?id=JjQrpYswtYEC&q=impredicative&utm_source=gb-gplus-sharePhilosophy of Mathematics