whether the reason for this difference is the very essence of the existent, an attribute it possesses, or something else. No one who understands this disputes it. If the ground for the possibility of being seen is exclusive to what exists, it must be either something shared by all visible things, whether substances or accidents, or something peculiar to some of them. The second alternative, however, is false, for a shared property must have a shared cause. If its cause were peculiar to some of them, the property would exist both when that cause was present and when it was absent. The property would therefore not depend upon it. Rather, that attribute would have no causal efficacy and no influence on the property’s existence, since the property exists in its absence just as it does in its presence.

This is clear. We have already drawn attention to it in our earlier discussion of tamāl concerning causes and effects. We also discussed counterexamples and the absence of causal efficacy, and explained the distinction between a complete cause, which cannot be divided, and an incomplete cause. Accordingly, seeing any