“If he were human by virtue of his very essence, then ʿAmr would not be human by virtue of his own essence.” What, exactly, do you mean by “his being human”? Do you intend an absolute, shared humanity, or the particular humanity that belongs to him alone? On either supposition you will find (1) the same division within his essence. If what you have in mind is humanity in the abstract, then set opposite it his essence taken in the abstract; but if what you intend is his determinate humanity, then set opposite it his determinate essence. The absolute must be paired with the absolute, and the particular with the particular. In that case your statement, “If he were human by virtue of his essence, ʿAmr would not be human by virtue of his essence,” falls apart. For each of the two humanities (2)—if the determinate instance is meant—possesses a determinate essence that accompanies it in particularity; and if the absolute is meant, it possesses an absolute essence that accompanies it in generality. Thus “man” and the individual human essences are concomitant both universally and particularly. Your error lay in coupling a determinate humanity with an absolute essence, and that has no more right than the opposite move: positing an absolute humanity alongside a determinate essence. This is nothing but countering falsehood with falsehood and matching one error with another; and if the latter is false, so too is their statement.
It is often profitable in dialectic and debate to construct an analogue of an opponent’s claim; once that analogue is shown to be false, the rule that like cases receive like judgments makes it clear that its counterpart is likewise false. Matters are unveiled through such illustrative examples, and Allah has indeed set forth parables for His servants in His Book—they are among the most beneficial means of clarification.
Third aspect: They say, “Humanity is multiplied by the multiplication of the matter that bears it, and its attachment to matter is an effect that does not pertain to the very essence of humanity.” We reply: If by ‘matter’ you mean