Mark , I’m with you all the way on preserving the special protection for religion in law. But I don’t see any difficulty in acknowledging that you can have religion without God, and especially without a specifically theistic conception of God. Is Hinduism not a religion? Buddhism? There is an argument to be made that, for example, some forms of Buddhism are not religions because they deny the supernatural altogether, but that is not the dominant view and to my knowledge never has been, so the burden of proof would be on the person advocating that view; we certainly shouldn’t ask judges to interpret the law based on idiosyncratic meanings of words.
To my mind, the question should not be “what is a religion in general?” but “what makes something a religion for purposes of law?” Behavior would seem to me to be more important than metaphysics.
Granted, giving full weight to the real diversity that exists in human religion makes preserving religious freedom difficult. I think it’s preferable to admit the difficulty than to deny that any non-theistic belief systems are religions.