What vacuum? Taking away supernaturalism doesn't leave a vacuum. But if it did, how about filling it with rationality?
Much easier said than done, Chairman Bill. Some of the greatest scientists and rational thinkers have professed a belief in some sort of God, including Albert Einstein, although Einstein's belief seems to have been more along the lines of Intelligent Design rather than a belief in a personal deity who intervenes in human affairs.
Voltaire was a fairly rational and enlightened sort of guy, wouldn't you agree? Yet one of his most famous sayings is, "If God did not exist, it would be necessary to invent him."
Be careful now, lest Judgement Day be upon you.
(Attached image was processed on my Dell Notebook. Not sure about color calibration, so if it looks a bit odd, that's the explanation.)