The first point is to understand what is to be implied in the term “soul.” Plato was really a dualist in that he regards the soul as a separate entity which animates the body and compares it to a rider directing and controlling the horse he rides. But Aristotle makes a more careful analysis of psychological phenomena. In the treatise _de anima_ he says “there is no need to enquire whether soul and body are one, any more than whether the wax and the imprint are one; or, in general, whether the matter of a thing is the same with that of which it is the matter.” (Aristot: _de anima_. II. i. 412. b. 6.) Aristotle defines the soul as “the first actuality of a natural body having in it the capacity of life” (id. 412. b. 5), in which “first” denotes that the soul is the primary form by which the substance of the body is actualized, and “actuality” refers to the actualizing principle by which form is given to the body which otherwise would be only a collection of separate parts each having its own form but the aggregate being without corporate unity until the soul gives it form; in this sense the soul is the realization of the body (cf. Aristot: _Metaph._ iii. 1043. a. 35). A dead body lacks this actualizing and centralizing force and is only a collection of limbs and organs, yet even so it is not an artificial collection such as a man might put together, but “a natural body having in it the capacity of life,” that is to say, an organic structure designed for a soul which is the cause or reason of its existence and which alone enables the body to realize its object.