 It remains true, however, that Aristotle’s ideal presentation of a scientific explanation is that of a demonstration from first principles. Only such a demonstration, he believes, would make clear the necessary connection that constitutes a causal relation. While he recognizes that this ideal is not always attainable, it remains a desideratum. So how does one arrive at those principles? It is here that Aristotle’s empiricism seems on shaky ground. The active properties to which scientific demonstrations appeal are universals: they are properties common to all beings of a particular kind which constitute them as beings of that kind. Aristotle rejects the idea that such universal properties exist extra rem, independently of the individuals that embody them. So in order to arrive at the principles of scientific explanation we need to recognize the identity of kind among the forms of particular objects and thus the universal that is embodied in each of them (Owens 1966: 168). The process by which we come to grasp the universals required for scientific explanations is known as epagōgē (APo. 99b15–100b15), a term commonly (but unhelpfully) translated as “induction.”