Fourier Analysis and Spectral Theory

The final test of a theory is its capacity to solve the problems which originated it.

Analysis and natural philosophy owe their most important discoveries to this fruitful means, which is called induction. Newton was indebted to it for his theorem of the binomial and the principle of universal gravity.

During the period that began with classical Greece and ended with late pagan antiquity, philosophy was more than merely a theoretical discipline. Even when Aristotle identified philosophy with "theory," his purpose is to argue ... that a life of theoretical activity, the life of philosophy, was the best life that human beings could lead.