Any property has two sorts of causal features: “forward-looking” ones, having to do with what its instantiation can contribute to causing, and ldquo;backward-looking” ones, having to do with how its instantiation can be caused. Such features of a property are essential to it, and properties sharing all of their causal features are identical. Causal necessity is thus a special case of metaphysical necessity. Appeals to imaginability have no more force against this view than they do against the Kripkean view that (...) statements like “Gold is an element” are metaphysically necessary. (shrink)