I think this is where misinterpretation of thoughts come into play. I see what your saying wondering. But I also think I see what atpollard is seeing/thinking.
God does not command us to believe, as in we have to, even if we don't want to(which doesn't make sense really). But He does command it AS the only way to receive eternal life.
By definition a commandment is a "authoritative prescription". It is a conditional statement, without the ability of the one receiving it to alter it. The commandment is to believe, so we can either obey or disobey. We don't have the choice to "opt out" of the program.
Reminds me of a sad time when our church "split". I tried to talk them out of it, but too many hot heads. They took a 'vote of confidence' and much to my surprise there were 3 choices.
Confident
Not Confident
Those abstaining
Looking back its somewhat humorous, but I think I was the only one who stood up when they asked for those abstaining.
Point is, we cannot abstain from God's command. We either obey it or do not. Each way has an outcome.
Maybe atpollards point is if its not a 'command' then when we see the word belief or believes, then its just describing what the person has been predestined to do without choice. But since we can use reason, we can see that it is indeed a command, as John says, and thereby understand its a definite choice.