—that his proof entails this. Whenever this proof of his is valid, this much benefits him rather than harms him, for his proof would then establish two things: that you have made Him more contemptible than an indivisible atom and rendered Him nonexistent, and that He has spatial location and magnitude. It would thus establish both the correctness of his position and that your position entails that Allah is nonexistent. This follows from his admission that his proof entails the truth of that claim.
But if you say that his proof depends upon this being true—in the sense that, unless it is established that Allah has spatial location and magnitude, it cannot be established that, if He cannot be perceived by the senses or pointed to, He is smaller than an indivisible atom—then you have not established this; you have merely made an unsupported assertion. You would therefore not have answered the counterargument, which is what was required.
For he does not concede that, if we know that something cannot be perceived by the senses or pointed to, we cannot know it to be nonexistent until we first know that it has spatial location and magnitude. Rather, knowledge that it has spatial location and magnitude may come afterwards, beforehand, or simultaneously, if the two necessarily entail one another. This follows with particular force from your own principles and those of your companions, for you