Firstly, consider that all things which are actual are also possible. This should be obvious enough. Is there anything that is impossible but also actual? No. Impossible things, by definition, cannot be actual. So we can say that possibility is logically prior to actuality.

With me so far? OK.

Now, secondly, note that if something is impossible, then there is something else that explains why that thing is impossible. In other words, there is no brute impossibility. Impossibility always has an expl...