Among mathematicians in general, three main categories may be distinguished; and perhaps the names logicians, formalists, and intuitionists may serve to characterize them.
Felix KleinRegarding the fundamental investigations of mathematics, there is no final ending ... no first beginning.
Felix KleinIt is well known that the central problem of the whole of modern mathematics is the study of transcendental functions defined by differential equations.
Felix KleinThe greatest mathematicians, as Archimedes, Newton, and Gauss, always united theory and applications in equal measure.
Felix Klein