Counterfactuals

If Oswald didn’t shoot Kennedy, then someone else did If Oswald didn’t shoot Kennedy, then someone else did. If Oswald hadn’t shot Kennedy, then someone else would have.

If Boston had been in Alabama, then Boston would have been in a different place. If Alabama had encompassed Boston, then Boston would have been in a different place.

A counterfactual, A>C is true only if, and because, the closest world at which A is true is also one in which C is true.

If Oswald didn’t shoot Kennedy, then someone else did If Oswald didn’t shoot Kennedy, then someone else did. If Oswald hadn’t shot Kennedy, then someone else would have.