There are so many things wrong here that it would take a pretty long post to sort them. I haven’t the time or motivation at the moment so I’ll try to summarize.
William Lane Craig is a big exponent of the idea that there cannot be an infinite past. Why this is so important to his god belief eludes me. But whatever.
First, the Big Bang does not (necessarily) show that the universe had a start. Inflationary cosmology, which is well supported, argues that bubble universes are constantly forming and that this process has been going on eternally. Our (observable) universe is simply one bubble among infinitely many.
But let’s put that aside and suppose, for the sake of argument, that there is only one universe (ours) and that it “began” in the big bang. Now here is the Kalem argument of Craig.
Everything that begins to exist has a cause. (It is presumed god did not begin to exist)
The universe began to exist
Therefore, the universe had a cause
Now even we accept the above argument, it is far from clear that God
caused the universe to exist — still less a vengeful monster God that throws unbelievers into a lake of fire for eternity after they die for the “sin” of not believing he exists.
But does the above argument even work? Is it valid? Is it sound?
Well, it’s definitely not sound. P.1 is demonstrably false. In QM virtual particles pop in and out of existence with no cause at all, even in principle. P1 is therefore already wrong and the argument is unsound.
Is it at least valid? (conclusion follows from stated premises even if one or more of the premises is actually wrong).
No, it isn’t. The argument commits an equivocation fallacy. What do we mean by “begins to exist”? Do we mean, “begins to exist IN time,” or “WITH time”?
According to the big bang model, time began with
the universe. What this means is that under the big bang, the universe has always existed
even if it had a beginning! That is because there was no time before time.
From this there follows Craig’s composition fallacy: Even assuming it is true that everything that begins to exist has a cause (not true; see virtual particles, above), all that follows from this is that everything within
spacetime has a cause — it does not
follow that spacetime itself
must have a cause. Another way to see this is to say that the cause of everything in spacetime explains spacetime itself, just as the cause of each individual brick explains a brick wall.
Now remember, in modern physics, the universe has always existed
even if it had a beginning from the perspective of those inside the universe
(and where else would they be?). Always simply means “all the time that there is.” But put that aside and suppose the past is infinite in an absolute sense — that there is an actual infinity
of past events. Craig claims this is impossible. Is he right?
More later. I’m enjoying bitch-slapping Craig even though he did good work on Newcomb’s “Paradox.”
BTW, the notion that time exists only within
the universe was championed by Augustine of Hippo, many centuries before modern physics.