In reply we say to you: this division is broad and far from exhaustive. Your claim that the difference must lie either in existence and necessity or in essences does not cover all possibilities, for there is yet another case: that their divergence touches existence, necessity, and essence all together. Each of the two shares with the other the fact of having an essence that both exists and is necessary; thus they concur in the bare notions of existence, necessity, and essence, while they part company in the particular existence, necessity, and essence that belong to each of them alone.
Their difference in existence and necessity, moreover, is not—as you have imagined—that one is actually existent and necessary whereas the other is not. Rather, it is that the existence and necessity proper to this being are not the existence and necessity proper to that one. They share something and are set apart by something else; that very differentiation is what we call their difference. When one is distinguished from the other by its own particular existence and necessity, this is just like its individuation by its essence: its individual reality is marked off by its specific existence, its specific necessity, and its specific essence.
By contrast, it is impossible for one of them to be set apart from the other by absolute existence and necessity, for they share in those just as they share in the notion of essence. Whatever they share in common cannot, in principle, be what individuates one from the other. Since, then, your classification is not comprehensive, your proof is null and void.
Fifth point: Your assertion that “if they agree in existence and necessity, then—given what has already been shown—it is impossible for the essence or any of its attributes to be the cause of existence” is false. What is meant by “difference in essence” is simply that this entity has an essence peculiar to it, just as that entity has an essence peculiar to it, even while they share in the mere concept of essence; likewise, this one has an existence or necessity peculiar to it, and that one has an existence and necessity peculiar to it, even while they both