The opening paragraph of the Physics sketches succinctly Aristotle's general notion of scientific knowledge. First, in any scientific discipline, to know a thing is to know its principles or elements. Secondly, the natural path of human knowledge is from things that are more knowable for men to things that are more knowable in themselves, that is, from concretions to the distinct cognition of principles and elements. These two norms are regarded as applying to all scientific procedure. Here they are outlined briefly as an introduction to the Aristotelian philosophy of nature. But Aristotle goes on to apparently recommend moving from universal to particular. We here explore what that might mean in the context of Aristotle's philosophy and particularly at the beginning of the Physics.
Owens, Joseph C.Ss.R., "The Universal in Physics I.1" (1964). The Society for Ancient Greek Philosophy Newsletter. 44.