Friday, March 04, 2016

The Basic Reason to Reject Naturalism: Substantive Boundary Disputes

I've been trying to work out what I think the most basic reason to reject naturalism (about mind and morality) is.  Sometimes it's suggested that normativity is just "too different" from matter to be reducible to it.  (Enoch and Parfit both say things along these lines.)  But that seems a fairly weak reason: plants and stars seem very different from atoms, after all, but that doesn't stop them from being wholly reducible to atoms.  Granted, mind and morality are even more different, being non-concrete and all, but still.  I think the non-naturalist can do better.

So, a better intuitive basis for rejecting naturalism, it seems to me, is that it can't accommodate the datum that debates about the distribution of mental or moral properties are substantive.  Imagine two people disagreeing about precisely which collection of atoms constitutes the Sun. (There's overwhelming overlap between the two proposals, they just differ slightly in where they draw the boundaries -- whether or not to include a particular borderline atom, say.)  It's clear that this is a merely terminological disagreement: they diverge in whether they take the word 'Sun' to pick out the minimal collection S, or the one-atom-larger collection S*, but it's not as though there's some further issue at stake here about which they remain ignorant -- which collection of atoms has some putative special further property of really being the Sun.  There is no such further property.

Disagreements about the distribution of minds and moral properties are not like this. But if naturalists were right, they should be.  As I wrote in an old post on 'non-physical questions':
The question whether my cyborg twin is conscious or not is surely a substantive question: I'm picking out a distinctive mental property, and asking whether he has it. Now, the problem for physicalists is that they can't really make sense of this. They can ask the semantic question whether the word 'consciousness' picks out functional property P1 or biological property P2. But given that we already know all the physical properties of my cyborg twin (say he has P1 but not P2), there's no substantive matter of fact left open for us to wonder about if physicalism is true. It becomes mere semantics.

In other words, in order for it to be a substantive fact that consciousness tracks (say) functional rather than biological properties, there needs to be a further property (distinct from the functional and biological properties) for the two views to both be arguing about. Otherwise they're just arguing about a word.  But it's obvious that disputes about the boundaries of consciousness are not just disputes about the word (in stark contrast to disputes about the boundaries of the Sun).

Similarly in metaethics:

The whole problem for the naturalist is that they have no basis for claiming that any particular one of the competing, internally coherent moral theories is the one true moral theory. After all, given the natural (non-moral) parity between us and our Moral Twin Earth counterparts, what in the two worlds can the naturalist appeal to as the basis for a moral or rational asymmetry between us?

If moral boundaries are not just to be determined by arbitrary semantics, it must be that there's a metaphysical difference between the truly good properties and the pretenders, breaking the symmetry. There must be a further property of goodness for the rival views to be arguing about.

I think this is the core intuition that's really behind the Open Question Argument, Parfit's triviality and fact-stating objections, as well as the knowledge argument in philosophy of mind.  But I'm not sure if anyone has put the point in quite this way before?


  1. Nice post. Though, it's worth pointing out that the moral twin earth argument has been nicely criticized by Janice Dowell recently. Intuitions about what people on each planet "seem to be arguing about" may not be as probative as we think they are( You call this substantive disagreement a "datum" but it's not clear that a naturalist should accept this dialectical imposition.

    Second, in your post on MTE, you just say that idealized agents won't converge after reflective equilibrium, but I don't see an argument for that. The naturalist (i.e. Brink) has claimed that there will be convergence, and that the lack of current convergence is not evidence against this, since people are really bad at reflective equilibrium (an understatement). As I understand the dialectic, this is how the naturalist will say the One True Theory can be identified. Thoughts on why this line of response is mistaken?

    1. I don't think my above presentation appealed to any controversial claims about what people on other planets mean by their terms, though? (The way I appeal to Moral Twin Earth here is different -- less "semantic" -- than Horgan & Timmons' version.) So I don't think Dowellian skepticism about our grasp of hypothetical languages provides any objection to what I say here, as I have spoken in English throughout. If the naturalist is really willing to deny that normative and mental questions are substantive, then that's game over as far as I'm concerned. Whatever they think they're talking about, it's not what I'm interested in.

      "you just say that idealized agents won't converge after reflective equilibrium, but I don't see an argument for that"

      I guess it just seems clear to me (and others from Street to Parfit) that there are multiple possible internally coherent normative views. You can't necessarily argue the amoralist out of their view, any more than you can out-argue the counter-inductivist or the external world skeptic. Some false views are rationally impervious to correction. (Though, for the record, I'm not convinced that even convergence would suffice to save the naturalist: the 'substantiveness' worry can no longer be expressed in terms of multiple equally-eligible candidates, but the underlying worry would remain. We'd just have to work out a different way of expressing it.)

  2. Richard,

    While I don't take a stance on naturalism (the naturalist/non-naturalist dispute isn't clear enough to me), my impression on Moral Twin Earth is that they would be probably talking past each other. My alternative interpretation would be towards an error theory (at least epistemic), due to evolutionary considerations (but we've already discussed that in another thread).

    1. Clarification:

      Generally, I tend to think that as Vanitas suggested, the naturalist doesn't have to accept that there is substantive disagreement on that case.

      On the other hand, I do think that if there is substantive disagreement on Twin Earth, the naturalist is in trouble (but I think that would help the error theorist in the end, rather than the non-naturalist).

    2. Yes, I think the real debate in metaethics is between robust realism and error theory. Rejecting naturalism clears the ground for, but does not settle, that deeper issue.

  3. Really great post! Could the physicalist who is a robust normative realist say that there is a substantive dispute about whether the cyborg is conscious because the referent of 'conscious' is partially determined by which states are normatively significant. Then they'd get substantive disagreement in both areas for the price of one.

    1. True, but it would seem to get the order of explanation wrong: most plausibly, the normative significance of conscious pain stems from its distinctive nature (how it feels), rather than some state being painful because it matters normatively.

  4. plants and stars seem very different from atoms, after all, but that doesn't stop them from being wholly reducible to atoms.

    Where is the evidence that stars and especially, plants are wholly reducible to atoms?


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