Solution

Give up? Well, here’s the trick: premise 4 simply does not logically follow from premises 2 and 3. If I will not drink a root beer tomorrow, then it is entirely true that I can’t drink a root beer tomorrow in the sense that the law of noncontradiction dictates (because I can’t both drink and not drink a root beer at the same time). But this “can’t” only applies if I will not drink a root beer. It’s still quite possible for me to not drink a root beer because I use my free will to decide this outcome, not because I’m unable to do otherwise. All that the law of noncontradiction can say here in this matter is that I can’t simultaneously choose and not choose to do drink a root beer.

Another way to look at the problem is that the reasoning sort of confuses can’t with won’t. Suppose I will not drink a root beer tomorrow. This could be because I exercise my free will to choose not to drink a root beer. Of course, I can’t both drink and not drink a root beer at the same time because of the law of noncontradiction. So if I’m not going to drink a root beer, then I won’t drink a root beer. But it doesn’t follow that I won’t drink a root beer because I can’t. The sort of “can’t” the law of noncontradiction is only about having two contradictory propositions both being true, and using my free will to bring about a result does not necessarily contradict that principle, even when drinking a root beer.

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