How do you prove you’re not lying about your faith?

Jerry Coyne continues to suggest that President Obama is actually an atheist. He points to text from Obama’s book, Dreams From My Father, which demonstrates that Obama had reasons other than spiritual to join a church and start behaving like a Christian. That’s fair enough, but as Coyne admits,

Of course, there’s no way to adjudicate the issue—how can you look into his heart?

That is a very good question: how does one determine whether the President really believes in God? This is not a matter that can be measured or observed from the outside. Only Barack Obama knows what he believes. Further evidence for Prof. Coyne’s claim is:

Face it: none of us really knows what the man believes. Consider this, though: what if he really was an atheist, as his earlier history suggests, but also had a burning desire to be President? What would he do?  Pretend that he was religious, of course! Nobody who refuses to pander to the faithful could ever be elected President in this era. This fact immediately makes all the evidence for Obama’s “faith” suspect, like Michael Corleone assuring a Congressional committee that he’s just a simple importer of olive oil.

Well, that much is true: anyone who wants to be POTUS pretty much has no choice but to pass as a Christian. By that logic, how many of the previous 43 POTUSes were also covert atheists? Are we now going to sift through FDR’s early writings to seek evidence of godlessness? And if Obama really does believe in the Holy Trinity, how should he go about proving to Prof. Coyne that he’s not just going through the motions for political reasons? Do all presidential candidates have to pass an audition to demonstrate their Christian credentials to the electorate? How does a politician prove a negative?