The confusion of actuated with actuable matter was quite unavoidable in the Aristotelic theory of substantial generations. This theory assumes that not only the primitive elements of matter, but also every compound material substance, has a special _substantial_ form giving the _first_ being (_simpliciter esse_, or _primum esse_) to its matter. Hence, in the substantial generation, as understood by Aristotle, the matter must pass from one _first_ being to another _first_ being. Now, the authors who adopted such a theory well saw that the matter which had to acquire a first being, was to be considered as having no being at all; else it would not acquire its _first_ being. On the other hand, the matter which passed from one first being to another was to be considered as having a first being; or else it would not exchange it for another. Hence the first matter, as ready to acquire a first being, was called a _pure_ potency--that is, a potency of being; whilst, as ready to exchange its first being for another, it was called a _real_ potency--that is, an actual reality. That a _pure_ potency can be a _real_ potency, or an actual reality, is an assumption which the peripatetic school never succeeded in proving, though it is the very foundation of the theory of strictly substantial generations as by them advocated. Before we proceed further we have to mention S. Augustine’s notion of _unformed_ matter, as one which contains a great deal more of truth than is commonly believed by the peripatetic writers. This great doctor admits that _unformed_ matter was created, and existed for a time in its informity. “The earth,” says he, “was nothing but unformed matter; for it was invisible and uncompounded, … and out of this invisible and uncompounded matter, out of this informity, out of this almost mere nothingness, thou wast to make, O God! all the things which this changeable world contains.”[27] Some will ask: How could such a great man admit the existence of matter without a form? Did he not know that a potency without an act cannot exist? Or is it to be suspected that what he calls _unformed matter_ was not altogether destitute of a form, but only of such a form as would make it visible as in the compound bodies?