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.
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.