Aristotle

“ For instance, the essence ‘animal’ is predicated of the essence ‘man,’ and it is true to say that every essential attribute of man is an essential attribute of animal, (just as it is true to say that every man is an animal) but not in the sense that man and animal are identical. ”

“ In fact, those who prove by means of a convertible proposition what is the essence of Soul, of Man, or of any other existing thing, are guilty of begging the question.
Thus, suppose it were asserted that the soul is a thing which is the cause of its own life, and that this cause is a number which moves itself. Here one would have to assume that the soul is like a number which moves itself, and is actually identical with it. A will not in fact be essentially predicable of C because A is a consequence of B, and B of C, though it may be conventionally so denoted ”

“ What man’s essence is; let C be ‘man,’ and A the essence, whether this be ‘biped animal’ or something else. If then a syllogism is to be formed, A must be predicated distributively of B, and further a middle term is required, and this will be predicable of the essence A. Thus one will be assuming what one ought to prove, seeing that B will also denote man’s essence. ”