Tuesday, September 27, 2005

Notes on Determinism, Modality and Causality

Below are some thoughts I was trying to develop. Everyone is welcome to point out where I'm getting off-base.

1. If determinism is true, there is no modality: everything is necessary. So, if you take modalities like possibility and contingency to be real, determinism is false.

2. If determinism is true, there is no “real” (non-Humean) causality: everything is connected necessarily and symmetrically; the world is fixed forever. Real causality implies modality: things could have happened differently if causation is assumed to involve real “work”. Like modality, real causality is opposed to determinism.

David Lewis would be able to embrace both modality and determinism by postulating concrete possible worlds (which are causally unconnected to ours) as the vehicle for modality. But he is a Humean about causality. There is no real causation in his system.

The only way to embrace modality and real causation is to reject determinism. This implies that the world includes an intrinsic selection or choosing among possibilities within causal events.

An assertion that only objectively random choosing occurs at this point is ad hoc: it has no particular advantage over asserting that choosing is non-random.


Gregg Rosenberg said...

Hi Steve,

A couple points on (1): Philosophers usually recognize different grades of modality. I think you are equating natural possibility with possibility tout court, which lots of people would not do. Also, your conclusion follows only if the world's initial state was also necessary. If the world's initial state was contingent, then even if determinism is true there are other naturally possible worlds.

On (2): If you have in mind the discussion about real causality entailing real possibility that I put forward in my book, note I say that argument is not valid in the "limit case", which is determinism.

Steve said...

Thanks Gregg. I'm new to thinking about modality, and I guess I'm only considering a simplistically strong realist concept here.

I think I understand your last point (although I can't immediately locate the relevant passage in the book). If real causality were truly implemented at the micro-level of nature, there is no contradiction between determinism and causality -- it's just that we have reason to infer this is not true of our world, and that a richer set of indeterminancies exist at multiple levels. (?)

Gregg Rosenberg said...

The argument I was referring to is in chapter 10, right before I begin discussion of space, time, and the unity of the world. I don't have the book in front of me, so I can't give you a page number. Anyway, with respect to that argument, your thought above is right: One can only reconcile realism about causation with irrealism about possibility if determinism is true. But we shouldn't think determinism is true (and, more subtly, we shouldn't think determinism *has* to be true), so we shouldn't be irrealists about possibility.

There might be a different argument than the one I give that shows determinism and realism about causation are somehow incompatible. I just wanted to point out that my argument didn't go that far, in case you were mulling that argument over.

Steve said...

Thanks. Yes, it's part of your excellent section 10.4 on the metaphysics of possibility. For another view which is similar I recalled I had seen this paper by Carl Hoefer. I reread it, and while the arguments don't seem to be completely knockdown, it's also pretty persuasive to me.

I wonder why all these philosophers spend time on compatibilism of free will and determinism and related topics when determinism has seemingly no adequate metaphysical basis?