I'm very open to a higher power, of which there could very well be one. But as of right now, I see no actual proof. And neither do you.
You can't know that because you cannot know what BTM knows or has experienced. You can only speak for yourself when it comes to matters of faith and experience. You have no information or authority to tell him what he does and does not have as proof of anything.
My experience is proof that I saw my shadow on the sidewalk this morning. But I cannot prove that I was outside or saw my shadow to another living soul because nobody saw me outside this morning. Just because it is overcast on your street one block over, does not mean that the sun did not break through on mine. We should be very careful of dictating to somebody else what he or she is required to believe.
But you say you are open to the possibility. Would you be willing to put it to the test? Ask God to make himself known to you? And put absolutely no restrictions of any kind of when, how, or in what form he does that? This is an exceedingly difficult thing for most especially highly intelligent people to do. But it is worth the effort.