 Jenkins and Nolan (2012) argue that disposition ascriptions are hyperintensional. Heidi the gifted mathematician may be disposed to find the proof of a given conjecture, on condition that it has one. This disposition of Heidi’s can be known in advance of knowing whether the conjecture has a proof. (“Give this to Heidi: if there’s a proof to be found, she’ll find it”.) Suppose the conjecture is in fact false, though the mathematical community does not yet know that. Then the condition of the disposition ascription is impossible. Still, we cannot substitute any impossibility in the disposition ascription. It is plausibly false that Heidi is disposed to find the proof of that conjecture, on the condition that she was always both identical to the number 7 and innumerate, for example.