Hippolytus

“ As regards, however, the Deity, the Originator of all those glorious objects in creation, (the nature of) this (First Cause) —even to one conducting his speculations by a more prolonged inquiry than that concerning (the soul) —is more difficult to know than the soul itself. The definition, however, which Aristotle furnishes of the Deity is, I admit, not difficult to ascertain, but it is impossible to comprehend the meaning of it. ”

“ And another peculiar dissertation has been (written) by him, entitled Concerning a Fifth Substance, and in this work Aristotle unfolds his theological opinions.
There exists some such division of the universe as we have now attempted to delineate in outline, and (corresponding with it is the division) of the Aristotelian philosophy. His work, however, (styled) Concerning the Soul, is obscure. For in the entire three books (where he treats of this subject) it is not possible to say clearly what is Aristotle’s opinion concerning the soul. ”

“ For, as regards the definition which he furnishes of soul, it is easy (enough) to declare this; but what it is that is signified by the definition [4] is difficult to discover. For soul, he says, is an entelecheia of a natural organic body ”