 A second form of justificatory empiricism holds that some beliefs can be defended only by reference to experience, there being no arguments from prior principles that can be adduced in their support. These include, first of all, matters within the domain of the other sciences which mere reasoning could never have revealed, such as the practical discoveries made by alchemists (Bacon OM 6, 2a prae.). But there are also matters that fall outside the domain of any speculative science, fields of inquiry in which scientia experimentalis “by its own power investigates the secrets of nature” (Bacon OM 6, 3a prae.). To appreciate what this kind of investigation entailed, we need to understand the class of phenomena to which it applied: that of the secrets of nature.