- To
issue a genuine command requires that you make an honest effort to
make the recipient aware that you are the one commanding them (such
that a rational person would recognize the authority and authenticity
of this command).
- God is
omnipotent, and thus does everything he makes an honest effort to do.
- Therefore,
if God has issued someone a genuine command, then he must have made
them aware the he is the one commanding them. [1&2]
- But if
a rational person is aware that God is commanding them, then they are
aware that he exists.
- Therefore, if a rational person is not aware that God exists, then they have not been issued any commands by God. [3&4]
And of
course from (5) it follows that, on divine command theory, rational
non-believers have no obligations and can do no wrong. But that's
absurd: atheists have obligations just as much as anyone else, so
there must be some flaw in the argument. Premise (2) and (4) seem
indubitable, so it all comes down to rejecting (1) or rejecting
divine command theory.
But
premise (1) is very plausible. Imagine getting mailed a note from the
government, written in pencil on loose leaf paper, without any
official markings, and no name signed at the bottom saying, "you're
summoned for jury duty, show up at the court house next Thursday
morning". You would throw the paper away immediately, and it
would seem rather silly to think you were the recipient of a genuine
command, or that you had any obligation to obey. If the commander
hasn't even tried to issue the command in such a way that a rational
recipient would recognize its authenticity then, though the
commanders will has been expressed, this expression doesn't seem to
amount to a genuine command. But of course this is what scripture or
religious tradition looks like to rational non-believers, and they
will be very justified in doubting the authenticity of purportedly divine commands.