 [The] power of nature is so ample and so vast, and these principles [sc. the laws of nature] so simple and so general, that I notice hardly any particular effect which I do not know at once that it can be deduced from the principles in many different ways; and my greatest difficulty is usually to discover in which of these ways it depends on them. I know no other means to discover this than by seeking further observations whose outcomes vary according to which of these ways provides the correct explanation (AT 6: 64–65, CSM 1: 144).