No idea is really bad, unless we are uncritical. What is really bad is to have no idea at all. - George Pólya

For many of the stories told the final form resulted from a sort of informal psychological experiment. I discussed the subject with several different classes... Several passages... have been suggested by answers of my students, or... modified... by the reaction of my audience.

A great discovery solves a great problem, but there is a grain of discovery in the solution of any problem. Your problem may be modest, but if it challenges your curiosity and brings into play your inventive faculties, and if you solve it by your own means, you may experience the tension and enjoy the triumph of discovery.

teaching of calculus to engineers and physicists, could be essentially improved if the nature of heuristic reasoning were better understood,