Paul Manata quoted an objection to libertarianism by Peter van Inwagen:
The basic idea is that if an agent is free in the libertarian sense, then no antecedent condition determines the outcome—so that if you repeat the past, then, sooner or later, the agent would have done otherwise. I’d like to briefly elaborate on the implications of this position.
1.Traditionally, libertarianism involves the axiomatic assumption that I can’t be held responsible for my actions unless I was free to do otherwise.
But as Van Inwagen shows, libertarianism is far more radical than it would initially seem to be. For the logic of libertarianism is not merely that I *could* have done otherwise, but that I *would* have done otherwise. Not merely that I’m free to make either choice, but that I opt for both.
In other words, there’s a possible world in which I leave Keilah, and another possible world in which I stay in Keilah. That’s what it means to have libertarian freedom. That’s how the freedom to do otherwise cashes out. There is a possible world corresponding to each choice. A possible world in which I exercise each option. I didn’t choose one over another. I did both—but not in the same world.
2.This, in turn, raises the question of what individuates the real world from a possible world. What’s the differential factor? Why is only one of my possible choices exemplified in the real world? Or, to put it another way, why do I find myself in a world where I make one choice rather than the other?
Obviously I didn’t instantiate this scenario. For if my choice is what actuates a possible world (or world-segment), then there would be more than one real world (or world-segment) since I make different choices in different possible worlds.
3. So some other agent or agency must be behind which choice of mine sticks. Which possibility plays out in actuality.
For I didn’t get to choose which choice would make the final cut; which choice, out of all the alternative choices which I made in different possible worlds, would be concretely exemplified in space and time. I didn’t get to choose which possible world would become the actual world.
But where does that leave the libertarian assumption about the preconditions of personal responsibility?
4.This, in turn, goes to the question of how the future comes to be. How does the future eventuate?
According to libertarianism, the past does not determine the future. Rather, the agent is in some measure the creator of his own future—and thereby his future existence.
Yet libertarianism doesn’t say that I’m the source of everything that happens to me. I didn’t cause myself to still have a body a minute from now.
So libertarianism has an oddly honeycombed view of existence, as if parts of reality are determined by the past, while other parts are blank spaces waiting to be penciled in by the agent.
This is a very peculiar view of reality. I originate part of my future reality, while other parts are caused by something else. Although I can’t actuate my body from one moment to the next, yet somehow I’m able to actuate other eventualities. I better be careful where I step lest I fall into a hole of nothingness.
5.But it gets even stranger. Not only do I, as a libertarian agent, create a part of my own future, but I can create a part of your future as well. For some of my choices negate some of your choices.
If, for example, you and I both love the same girl in high school, but I’m the one who captures her heart, then I end up creating a very different future for you than you would have chosen had you married her instead of me. (And remember that there’s a possible world in which she does become your wife.)
In that respect, I created your future. Indeed, I created the future you. The person you will be. The future in which you will exist. You would still exist, but apart from my choice, you would not exist in that particular future.
6.As a result, libertarianism confers godlike powers on the agent. Godlike power over his fellow agents. I can enact your future, or parts thereof, without your consent.
But, once again, it’s hard to see how this does justice to the libertarian preconditions of responsibility.
7.In that respect, there is a sense in which, according to libertarianism, the past determines the future. By my past action, in winning the hand of the woman we both wanted to marry, I end up determining a different future for you than you would have chosen for yourself.
But, once more, it’s hard to see how this does justice to the libertarian preconditions of responsibility.