Determinism can’t have possible worlds

Why do things happen? It may seem obvious that everything happens because of something else. Any thing that happens — that is, any event — is also an effect.

If we assume everything has a cause, there are many philosophical/metaphysical consequences that ensue. From here we could go to a formulation of the cosmological argument (being itself must have an uncaused cause), or perhaps we could consider what this means about our freedom of choice. After all, if everything has a cause, so do our actions. That may not seem problematic, until we consider things further.

Looking at things at first glance, I might think: so what? My actions have causes, of course. Their causes are my decisions do act. How does that conflict with my freedom of choice? But then we go further: If everything has a cause, so do my decisions to act. Why did I choose this instead of that? From here, we may look into neurochemistry or into reasons. If neurochemistry is the reason why we decide, then we are not really in control.

But reasons seem to do it. But then again, why these reasons? What is the cause for me being compelled by some reasons and not others? If there really is a reason, then eventually it will lie outside of my control. The only way for it to lie within my control would be if there were no reason at all. If my decisions were result of mere caprice. But why does my spontaneous mind favours this rather than that?

If there is no reason at all, than we are talking about arbitrary events. Randomness is not our ideal of control either, I suppose. Not only that, but it seems that if anything is to have any explanation at all, than it is necessary that it be a full explanation. An explanation that leaves a bit of the explanandum unexplained does not seem like such a good explanation after all: we can always ask about the why behind that unexplained bit.

This means that, either everything has an explanation that accounts for events in their totallity, or nothing has any explanation at all. Either things have causes, or they don’t. Because if some do and some don’t, then why is it that they don’t? If we explain this, we will end up having an explanation for these events, which will mean that they are not unexplainable as we thought.

So if anything has a cause, everything has a cause. And if that is true, than everything we do is determined. Not only everything we do, but everything that happens, ever. Putting this in other words: everything that happens, happens necessarily.

One consequence this has is the denial of possible worlds. These are common in philosophical discourse. We call some things contingent if they happen in some possible worlds and not in others. This means they could have happened, but did not, or could have not happened, but did. On the other hand, necessary events are the ones that happen in every possible world. And impossible events are the ones that happen in no possible world.

But if everything that happens, happens necessarily, than there is no contingency. Either an event is necessary, or impossible.

There is no world where that stone falls just a few centimiters to the side. No world where I didn’t say that hurtful thing. No world where I had a career as a prize fighter. No world where my heartbeat was in any minuscule way different than what it actually got to be. Any of those worlds is literally impossible. Metaphysically impossible, at least. There are no possible worlds except the one. There is only one “just so” world that could have happened, and did. Any other world, though logically conceivable, is metaphysically impossible.

This seems to imply that logical possibility is broader than metaphysical possibility. Which apparently means that logic constrains metaphysics, instead of the other way around. The funny thing is, we only get to this conclusion because of the acceptance of a metaphysical principle — namely, that everything has a cause.