Suppose that the universe began with the Big Bang, and the Big Bang had no cause, so the universe came into existence ex nihilo. It then went through many (infinitely many if time is continuous) stages—the one-second-old universe, the ten-second-old universe, the five-minute-old universe, the one-year-old universe, the 7-million-year-old universe, before arriving at the present 13.7-billion-year-old universe, and then (presumably) going onward.
Question: Why did the universe start in the Big Bang state rather than in one of these many other states?
Assuming the universe has no cause, there does not seem to be any compelling reason to think the Big Bang state is somehow “more likely” as a starting state of the universe. (If anything, it seems a less likely state, because it has lower entropy than the later states.)
Now, granted, if the universe started in a sufficiently “late” (as compared to our state) stage, there would be no observers in that universe other than perhaps Boltzmann brains, due to the universe having expanded too much. So we have an interesting bit of fine-tuning: the universe started in a sufficiently early stage that there was still time for life.
Let’s ignore that otherwise intriguing observation, however, and push ahead. Let St be the t-units-of-time-past-Big-Bang stage of a universe like ours. And let’s ask:
- Conditioning on all our observations, and given that the universe has no cause, is it more likely that the universe starts with S0 (i.e., starts with the Big Bang) than with, say, St1, where t1 > 0?
If the answer is negative, then the supposition of a causeless universe leads to a skeptical hypothesis: we have no more reason to think the universe started with the Big Bang than that it started in the t1 stage.
The answer may be positive in some cases. As we already saw, if t1 is past the time of there being any observers—or just past the time of there being any observers making observations like ours—then we can be sure the universe didn’t start in St1.
If it turns out that evolutionary is logically necessary for consciousness, as some materialists think (because, basically, evolutionary history is necessary for defining proper function for making functionalism run), we might get a positive answer if t1 is so close to the present that there was insufficient evolutionary history for our consciousness if the universe started at t1.
But if t1 is any time between 0 and about 3.7 billion years ago, our observations do not differentiate between the hypothesis that the universe started with S0 or that it started with St1. Thus, the answer to the bulleted question above is negative. Moreover, it’s negative for each of the many t1 in the relevant range (more than 0 but less than about 10 billion years). Thus, on a no-cause hypothesis we should not prefer the Big Bang hypothesis over a whole bunch of skeptical hypotheses holding that the universe started in a more developed form.
This argument will please theists who think the universe had a cause. Of course, the theist still has to find a way to give a positive answer to the bulleted question. I think there are two ways of doing so. First, likely a perfect being would have a preference for greater creaturely participation in creation, and creating the universe in, say, the 10 billion year stage, or indeed in any post-Big Bang stage, would pointlessly cut short creaturely participation in creation (e.g., in the 10 billion year stage, the Solar System would be created ex nihilo, rather than being generated from a star-forming nebula). Second, such a being would be likely to create a world that doesn’t make true what is intuitively to us a “skeptical hypothesis”.
The argument will also please the now-less-common atheist who thinks the universe is eternal.
