Back at home, he strove to recollect the theory of Newton as it was being taught in schools and universities – namely, that ‘colours in their totality are contained in light’. Hitherto he had had no occasion to doubt the correctness of this theory. Like everyone else, he had heard it expounded in lectures as an incontestable result of empirical observation, though without this ever having been shown to him by way of experiment. He convinced himself by consulting a manual that his recollection was correct, but at the same time he found that the theory there set forth gave no help in answering his questions.⁵ So he decided to examine the phenomena for himself.