Regarding the fundamental investigations of mathematics, there is no final ending ... no first beginning.
Felix KleinEveryone knows what a curve is, until he has studied enough mathematics to become confused through the countless number of possible exceptions.
Felix KleinEvery one who understands the subject will agree that even the basis on which the scientific explanation of nature rests is intelligible only to those who have learned at least the elements of the differential and integral calculus, as well as analytical geometry.
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 Klein