Help me know if I have the Big bang theory down correctly. It consists of the following ideas. 1. The big bang theory is usually or often seen as a naturalistic hypothesis where only physical reality is truly real. 2. The universe is a physical reality. 3. There was no physical reality prior to the universe. 4. The universe began with the Big Bang. 5. There was no universe (or physical reality) prior to the Big Bang. 6. It follows from 1-5 that nothing whatsoever existed prior to the Big Bang. 7. The objection of so how did the universe come about if there was nothing prior to the big bang is that time only began with the big bang. To speak of a beginning implies an occurrence within time. It is therefor circular to say that time began with the beginning(of time). I think that what is happening here is that a rejection of (traditional metaphysical)philosophy and even common sense means that science has become a new form of irrational religion in our day. What do you philosophers have to say about this? And who else besides me has noticed a circularity within the idea that time began at a certain point?

I'd say that you don't have the Big Bang theory down correctly if by the Big Bang Theory you mean what physicists mean. Whether a physicist accepts some version of the Big Bang account as a piece of physical cosmology and whether the physicist believes that nothing is real except for the physical are two different questions. Some physicist (perhaps even most for all I can say) believe that there's nothing outside the physical, but that's not a claim within physics. It's a metaphysical claim that the Big Bang hypothesis doesn't settle.

But suppose we're physicalists (i.e, suppose we think only the physical is real.) Is the combination of physicalism and the Big Bang inconsistent?

I don't see why.

You say that to speak of a beginning implies an occurrence within time. Let's concede that; it's logically harmless. The first moment, if there was one, was, of course, a moment in time. If time began, it began with the beginning; we can agree that this is circular (or better: a tautology.) But "Time had a beginning" is not a tautology at all, and the claim that there were no moments before the big bang is anything but circular. (It may be false; that's a scientific question. But the very fact that it could be false is proof that it's not a tautology.)

The idea that there was a first moment is peculiar the first few times you hear it. Once you get used to the fact that modern cosmology routinely appeals to space-time structures that are mathematically well-understood but not what Newton - let alone Euclid - had in mind, the oddness tends to fade away. No contradiction follows from saying that there was a first moment, and even on its face, the claim doesn't seem circular. The fact that "common sense" finds this odd doesn't tell us much; there's a great deal of respectable science that common sense finds odd, but then common sense didn't cut its teeth on the sorts of far-from-common situations that science has taught us to deal with.

Read another response by Allen Stairs
Read another response about Physics