Yet Hume raises radical skeptical doubts about this very principle. It has no foundation in reasoning: neither in demonstrative reasoning nor (on pain of circularity) in inductive reasoning itself. Nevertheless, as firmly based in custom or habit, it is a universal principle of the human mind. Moreover, it is also the foundation for the best available science of matters of fact—Newtonian inductive science—and for Hume’s own inductive science (self-consciously following Newton) of human nature.[