How can we ever talk about what would be?
If a statement A is assumed, that's not actually true, then anything would follow since a conditional with a false hypothesis is always true. But anything (such as "P and not-P") can't be true.
This seems to show that a statement that is not true would never be true to begin with. Thus, we can't talk about what would be, only what is.
For example, I'm not driving to the store. But if I were, I'd also be swimming. Of course, though, I can't drive to the store and swim at the same time. This comes to show that so long as I'm not driving to the store, we can't ever discuss the situation where I am driving to the store, since that situation implies a contradiction.