Determinism, as standardly understood, says:
- The state of the universe at any time, together with the laws, entails the state of the universe at later times.
Start with a world w with libertarian free will but where everything other than libertarian free actions is deterministic. In other words, free actions are the only loci of indeterminacy. Moreover, the laws of nature in w entail that exactly one finite agent ever makes a free choice, and there is exactly one free choice made by her and it is between a good and a bad option. Finally, the laws are such as to entail a finite age to the universe and to entail that the the one finite agent comes into existence some time after the beginning of the universe.
Now, consider a new world w* made by starting with w and appending an isolated part of the universe and some new laws. The new laws say that if the one finite agent chooses rightly, this backwardly causes the isolated part of the universe, from the beginning of the universe's existence, to contain exactly one riggle, a new kind of fundamental particle, while if the one finite agent chooses wrongly, this causes the part of the universe to contain exactly one wroggle, also a new kind of fundamental particles. Moreover, the laws prohibit riggles and wroggles from ever ceasing to exist, and from coming into existence in any other way. Moreover, riggles and wroggles, by law, don't cause any significant effects in any other matter, and in particular cause no effects that could lead to a causal circularity, and they behave deterministically.
If w was deterministic except for free choices, w* will be fully deterministic: the state of w* at any time, together with the laws at w*, entails everything that happens at later times. For the only possible place where there is indeterminacy is with regard to the agent's choice, but what the agent chooses is entailed by whether the isolated part of the universe contains a riggle or a wroggle at an earlier time.
However, introducing backwards causation and a riggle/wroggle does nothing to render the agent unfree. Hence, it is possible to have free will and determinism.
Note that time travel seems coherent, and if time travel is coherent, a fortiori so is backwards causation.
Now, does the above settle the question of compatibilism? No. For even though the above does make it very plausible that free will is compatible with determinism in sense (1), this only shows that the question was poorly phrased. For the relevant kind of determinism that threatens free will is not (1), but something like:
- Every action or choice A by every finite agent is causally necessitated by a state of affairs E that does not include in itself the agent or any of her intrinsic properties.
- A causally necessitates E only if (a) A is causally prior to E and (b) the proposition that A occurs conjoined with the laws entails that E occurs.
A different approach would be to keep (1) as the definition of determinism and then define compatibilism as the view that the following are compossible:
- A finite agent is free.
- Determinism holds.
- The laws rule out backwards causation.
6 comments:
What about the objection that indeterminism in regards to free will (but also in general) violates the Law of Identity? It's often said that if time were reversed and replayed, the agent could have chosen differently in the same circumstances and with the same reasons - but if taken in one sense this seems incoherent, since choosing A is different from choosing B, so if the exact same choice is replayed again, it stands to reason the agent would choose A again, as it's the choice is self-identical.
Furthermore, where would the difference lie in an indeterministic system where the same cause with the same external and internal context can cause different effects? We don't want to say that causing effect A is the same exact thing as causing effect B, so if they are different - and the Principle of Identity requires this much - then they can't be the same cause having different effects since the particular instances are different.
So how do we say that the same identical indeterministic cause - same both internally and externally - can cause completely different effects in the same external and internal circumstances without violating the Law of Identity?
Why not say that the cause of A is identical with the cause of B? Compare this. In one world, Socrates is Plato's friend. In another, he is Plato's enemy. So, Socrates' friend is Plato's enemy. That seems contradictory, but the contradiction is just as much apparent as in your case. Socrates is Plato's friend in w1 and Plato's enemy in w2. Similarly, the same event is a cause of A in w1, and a cause of B in w2. We give different names to the event in the two worlds, but it is the same event.
The argument isn't about the particular cause of A, but the very causing of A. And so this opens the question - what's the difference that makes the same event be the cause of A in w1 but in w2 is the cause of B?
What internal difference is there? And if there is one, what accounts for that difference between worlds? What makes the causing of A be what it is specifically, in contrast to the causing of B?
Now yes, some causes can have different effects - but it seems that for indeterminism the reason why there are different effects can't be due to internal or external differences; otherwise we would have contrastivity.
So the objection goes that if we want to have the same cause that is absolutely identical internally and externally causing different effects, we either need a difference somewhere - which seems to violate indeterminism - or there is no difference.
But the latter can't be true because of the Law of Identity and because the causing of A is distinct from the causing of B. So there must be a difference somewhere, which contradicts indeterminism because it requires that an event or cause could be absolutely the same internally & externally and still have different effects.
"The causing of A" is ambiguous between two things:
CA1: The event that is the cause of A.
CA2: The relation between the event that is the case of A and A.
CA1=CB1. And there is no contradiction. I don't see what you mean by the "Law of Identity". The cause of A is the cause of B. Where is the problem?
CA2 is indeed different from CB2. But CA2 is not the cause of A, nor is CB2 the cause of B. Indeed, CA2 is something that is explanatorily posterior to both the cause of A and A itself.
So the difference lies in the relation between the cause / event and the effect? But what exactly is the cause of that difference then? If it's something internal to the cause, that means there is an internal difference in the cause that distinguishes the causing of effect A from effect B - but this seems to undermine indeterminism as the cause isn't absolutely identical internally in both cases.
But if the difference is outside the cause, then what explains that? Are the effects caused by the relation or something external? In that case it makes no sense to speak of the cause being responsible for the effects.
How can the same cause with exactly the same internal state in both worlds end up making different effects? Is that even possible? What then accounts for the difference between them?
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