>Then why can't that thing be the universe?

Much of this background, I'm sure you know...

Science says the Unverse is expanding. If you reverse the process all matter comes back to a point such that the origin is the so-called Big Bang. Science also says the Universe is cooling, with no new energy being created. Had this gone on eternally (looking back in time), then why hasn't all the energy burned itself out by now?

Science doesn't explain where the matter in the Universe comes from (beyond the dense ball of matter just prior to the Big Bang). So, since there is so much still unexplained by science, there's a certain amount of faith/hope/uncertainty associated with whatever explanation you want to come up with.

The point is that those who claim a "pure" logic can't say they are any more logical than those who believe in God. In their mind, the existence of God sounds like a fairy tale, so therefore it must be a fairy tale.

Yet the Bible says this...

1 The heavens declare the glory of God;
the skies proclaim the work of his hands.

2 Day after day they pour forth speech;
night after night they display knowledge. (Psalm 19:1-2, NIV)

Essentially, the Bible appeals to an individual's common sense here.