rinciples of motion, from the many and varied ways of motion that occur in vulgar reality to the increasingly simple conception of the first motion of all, emanating from the unmoved mover.
In Physics, Aristotle builds his argument in stages. He provides a logical rationale for first principles, which is really his way of creating a rational framework for philosophical discourse altogether. He is looking for a way to discuss what is real in the natural world, and to do this without getting bogged down in precisely what is real about what is real, he says that what is may be actual or potential (Physics 327, et passim). Indeed, in order to avoid the trap of avoiding a clear definition of reality, Aristotle repeatedly makes the point that terms and conditions can be thought of in more than one way. The actuality or potentialty of existence, for example, is an important prelude to his statement that of whatever may exist, "some exist by nature, some from other causes" (Physics 328). Nature itself has two meanings. In one meaning, life forms and what are called the "simple bodies" (earth, air, fire, water) emanate from nature, while instances emanating from these, through some agency or art, are plainly "caused." In another meaning, nature may be considered as the "attributes" of a thing that makes it what it is. Aristotle is concerned to explore the content of the form that nature (or anything else) takes and the matter (attributes) of what occurs in nature: "The mode of existence and essence of the separable it is the business of first philosophy to define" (Physics 332).
At the center of this definition is the assertion that all existent things, natural or artificial, are subject to some category of change. This is so by reason of the fact that existence is either actual (which means existence was preceded by change) or potential (which means a new form of existence will come about because of change). Further, this potentiality or ...