From naturalism to divine command theory by way of vagueness

Plausibly:

1. There is a collection K of atoms forming an early stage of the developmental history of a particular human, where it is vague whether it is morally permissible to disperse the atoms in K.

Pro-choice readers might take K to be the collection of atoms in a late fetus or an early newborn. Pro-life readers might take K to be the collection of atoms at some early point during the fusion of gametes. (Note that (1) does not say that the atoms in K form a human.)

It is widely held that:

2. Vague matters always depend on semantic plasticity.

But:

3. Whether it is permissible to disperse the atoms in K does not depend on any semantic questions.

Claims (1)–(3) look incompatible. So we should abandon at least one of them. Personally, as a pro-life Aristotelian dualist, I am happy to abandon (1)—whether it is permissible to disperse the Ks depends on whether there is a human form uniting the Ks, and that’s not a vague matter. But apart from a Markosian-style brute fact view of composition—a view that seems implausible—it seems hard for a naturalist to deny (1).

Claim (2) is pretty plausible.

This means that if we accept (1), we should deny (3). But how to deny (3)? How could the question of whether it is permissible to disperse the atoms at some developmental stage depend on semantic questions? Surely it is a totally abhorrent idea that whether it is acceptable to disperse the atoms in K is determined by our linguistic performances?

Indeed! But it need not depend on the semantics of our linguistic performances. There is exactly one major moral theory that make that allows for a reasonable denial of (3): divine command theory. Commands are linguistic performances. Whether some act violates a command is in part a linguistic matter. Given divine command theory, semantic plasticity in the terms of the commands can ground vagueness in the obligations constituted by the commands. If your commander says: “Shave until you’re bald”, your obligation seems to be vague precisely because of the vagueness of language.

And that the semantics of God’s linguistic performances matters to the right to life of K is far from as objectionable as some claim on which our linguistic performances have the determining role. (Though our linguistic performances have some role to play, since they may help define the words that God is using if God speaks our language.) Thus, we can imagine that God says: “Thou shalt not murder.” But perhaps “murder” is vague. And the vagueness in this word then translates to vagueness as to whether the dispersal of the atoms in K is permissible.

If the above is right, then we have an argument for a very surprising thesis:

4. If physicalism (about us) is true, then divine command theory is the correct moral theory, and hence God exists.

This is yet another in a series of observations that I’ve been making over the years, that theistic naturalism has resources that its atheistic cousin lacks.

All that said, I think physicalism (even about us) is false, and divine command theory is not the correct moral theory. Though I do think God exists.