I was recently in a discussion with a Clarkian. In my judgement the traditional divine command theory seems demonstratively false. I explained my reasoning as follows:
(2) Moral values/duties are not grounded alone in God's will.
(3) Therefore, the traditional divine command theory of ethics is false.
Let's assume (1) entails:
(4) God can will any action or act to be morally blameworthy or praiseworthy. [i.e. volunteerism]
Further, if we affirm (4), with possible world semantics, it seems we are left with an implausible conclusion:
(5) There is a possible world which God wills adultery to be praiseworthy in all possible worlds.
(6) The actual world is a possible world.
(7) Hence, God wills adultery to be praiseworthy in the actual world.
Perhaps, this is a sloppy argument. But how does a Clarkian escape volunteerism? One possible way to avoid volunteerism from the traditional divine command theory is to adopt a modified divine command theory (e.g. Robert Adams); but it costs a philosophical price, it requires one to reject a robust doctrine of divine simplicity (i.e. the primacy of God's will: God wills His essence and His essence is His will; hence God's will and essence are one in the same qua divine simplicity). However, will a Clarkian deny a robust doctrine of divine simplicity to escape volunteerism?