The Consequence Argument: No Choice About the Future?

If we can't change the past and we can't change the laws of nature, do we really have a choice about the future? That's the intuition behind the Consequence Argument, one of the most influential arguments in the free will debate. It aims to show that if determinism is true, then every fact about the world, including every action you've ever taken, is something you never had any choice about.

The argument is associated primarily with Peter van Inwagen, and it has shaped the incompatibilist case for decades. It's also surprisingly rigorous. Where many free will arguments rely on intuition pumps, the Consequence Argument is built on formal logic. Let's walk through it.

The Core Intuition

The argument rests on two principles that seem hard to deny.

The first is the fixity of the past. What has already happened is settled. You can't reach back in time and change the state of the world in 10,000 BC. Whatever was true then is true now, and no one has or ever had any choice about it.

The second is the fixity of the laws. The laws of nature are not up to us. You didn't choose the gravitational constant. You can't decide that light should travel faster tomorrow. The laws of physics are what they are, and no one has any choice about that either.

Now add determinism: the thesis that the past plus the laws of nature are jointly sufficient to determine everything that happens, including every choice you make. If you combine these three claims, a troubling conclusion follows. The past was fixed before you were born. The laws were fixed before you were born. And together, they determine everything you do. So everything you do was fixed before you were born. You have no more choice about your actions than you have about the speed of light.

Two Rules

To make this precise, the argument relies on two inference rules.

Rule Alpha says: if something is necessarily true (true in every possible world, like 2+2=4), then no one has or ever had any choice about whether it's true. This seems obviously correct. You can't choose to make 2+2 equal 5. Necessary truths are beyond anyone's power to alter.

Rule Beta is the engine of the argument. It says: if no one has a choice about whether P is true, and no one has a choice about whether "if P then Q" is true, then no one has a choice about whether Q is true. In other words, powerlessness transfers across entailment. If you can't do anything about the premises, you can't do anything about the conclusion.

Here's an example to make this concrete. Diamond Jim and Calamity Sam are playing poker. Sam has a straight flush; Jim has two pairs. Jim has no choice about the fact that Sam holds a straight flush (the cards are already dealt). Jim has no choice about the fact that a straight flush beats two pairs (that's the rules of poker). So Jim has no choice about the fact that Sam's hand beats his. Powerlessness over the premises transfers to powerlessness over the conclusion. That's Rule Beta in action.

The Argument

Now apply these rules to determinism.

Start with the definition of determinism: necessarily, if you conjoin the complete state of the world at some time in the distant past (call it H) with all the laws of nature (call it L), that entails every true proposition P. In symbols: necessarily, (H & L) entails P, for any true P. (For example, P might be "The New Orleans Saints won Super Bowl XLIV.")

The argument proceeds in seven steps:

First, since the conjunction of H and L necessarily entails P, we can rearrange this by standard logic: necessarily, H entails that L entails P.

Second, by Rule Alpha, since this is a necessary truth, no one has any choice about it.

Third, by the fixity of the past, no one has any choice about H (the state of the distant past).

Fourth, by Rule Beta, combining steps two and three: no one has any choice about the fact that L entails P.

Fifth, by the fixity of the laws, no one has any choice about L.

Sixth, by Rule Beta again, combining steps four and five: no one has any choice about P.

And P was any true proposition whatsoever. So if determinism is true, no one has or ever had any choice about anything. Free will is impossible.

Objection 1: The Agglomerativity Problem

The Consequence Argument is valid if its rules are sound. So most attacks target Rule Beta. The most technical objection is that Rule Beta entails something called agglomerativity for the "no choice" operator, and agglomerativity is invalid.

Here's what that means. If Rule Beta is correct, you can prove that whenever no one has a choice about P and no one has a choice about Q, then no one has a choice about P-and-Q together. (The proof uses the fact that "if P, then if Q, then P-and-Q" is a necessary truth, then applies Alpha and Beta twice.)

But agglomerativity for "no choice" is false. Consider a fair coin flip. Let P = "the coin does not land heads" and Q = "the coin does not land tails." You have no choice about whether it lands heads (that's up to the coin), and you have no choice about whether it lands tails (also up to the coin). But you do have a choice about whether "it doesn't land heads AND it doesn't land tails," because you can just flip the coin and it will land on one or the other. So agglomerativity fails: no-choice-about-P and no-choice-about-Q doesn't entail no-choice-about-(P-and-Q).

Since Rule Beta entails agglomerativity, and agglomerativity is invalid, Rule Beta must be invalid too. Or so the objection goes.

The incompatibilist has two responses. The first is to replace the original "no choice" operator with a subtly different one: "P is true, and no one can or ever could do anything such that, if she did it, P might be false." This revised operator arguably blocks the agglomerativity problem while preserving the Consequence Argument. The second is to replace Rule Beta with a weaker version (Beta 2) that only transfers powerlessness across strictly necessary conditionals rather than all conditionals, which also avoids the coin-flip counterexample.

Whether these repairs succeed is still debated.

Objection 2: David Lewis and Local Miracles

The philosopher David Lewis offered a very different kind of response. Rather than attacking Rule Beta, Lewis challenged the fixity premises. Specifically, he argued that if you could have done otherwise, then either the past or the laws of nature would have been slightly different.

This sounds absurd at first. You can change the laws of physics? But Lewis's point is more subtle than it seems. Consider a concrete case: you didn't raise your hand at a department meeting to vote on a proposal, but you had the ability to. If determinism is true, then had you raised your hand, something in the causal history would have to have been different. Either the distant past would have been slightly different, or there would have been a tiny, localized violation of the laws of nature (a "local miracle") just before your decision.

The incompatibilist objects: if raising your hand would have caused the laws of nature to be different, then you're claiming an incredible, almost magical ability. Lewis's response is to drop the word "caused." On a Humean regularity theory of laws (where laws are just descriptions of patterns rather than forces that govern events), it's not that raising your hand would cause the laws to be different. It's that if you had raised your hand, the laws simply would have been different. No causation involved. The world would have had a slightly different pattern of events, and therefore slightly different laws describing that pattern.

The incompatibilist fires back: this gets the explanation backwards. You didn't have the ability to raise your hand at that moment. Rather, if the past or the laws had been different, that's what would have given you different abilities. The ability belongs to the history, not to you.

Why This Argument Matters

The Consequence Argument matters because it makes the incompatibilist case with unusual precision. It doesn't just gesture at the worry that determinism threatens free will. It formalizes it. And in doing so, it forces compatibilists to identify exactly which premise or rule they reject, and to defend that rejection rigorously.

The debate around Rules Alpha and Beta, the agglomerativity problem, and Lewis's local miracles is some of the most technically demanding work in all of philosophy. But the underlying question is as simple as the hook: if the past and the laws were set before you existed, and they jointly determine everything you do, then in what sense are your actions up to you?