Why do many philosophers consider a past-eternal universe to be self-explanatory but not a universe that began with no cause?

Question

In philosophical papers that argue against theistic interpretations, many philosophers fight to demonstrate that the Big Bang was not a true beginning but merely a transformation, arguing that the entirety of physical reality is beginningless, Quentin Smith and Graham Oppy being two well-known examples.

To my mind, this distinction appears pointless. What differentiates accepting a past-eternal universe without explanation from accepting a universe that began without explanation? Even a past-eternal structure requires an explanation for why it is as it is—for instance, why this particular structure can generate life-supporting Big Bangs rather than eternally producing lifeless ones.

This problem becomes even more evident if we consider the potential validity of the B-theory of time. Under this view, the distinction between a past-eternal universe and one that began is simply that one is a four-dimensional spacetime block with a boundary, while the other is a four-dimensional spacetime block unbounded in the past. In both cases, we are dealing with a 4D spacetime block existing in "nothingness" without any explanation for its existence.

It seems we have two options:

A) Accept the existence of brute facts. Here, we could accept the Big Bang as a brute fact that occurred without explanation, viewing it as a self-contained structure with nothing beyond it.

B) Reject brute facts altogether. In this case, a past-eternal universe is insufficient to explain why reality is the way it is. We must demand an explanation for everything, including why this specific past-eternal universe exists as opposed to any other possible past-eternal universe. Ultimately, this perspective could lead to something like Max Tegmark's Mathematical Universe Hypothesis, which posits that all possible mathematical structures exist as physically real universes, or an infinite hierarchy of meta-laws (which some philosophers argue is acceptable).

It seems pointless to me why many philosophers fight to argue that physical reality is beginningless yet accept a past-eternal universe without further explanation. If we are willing to accept brute facts, why not simply accept the Big Bang as a brute fact with nothing beyond it?

Answer 1

It may help to look at this in the broader sweep of history. The Big Bang is a relatively recent development in cosmology. The concept begins to appear in the early 20th century, but didn't really become widely accepted until roughly 1964. Prior to that, an eternal steady state universe was the more common assumption, among philosophers and physicists alike. With a steady state universe, there is no abrupt change 14 billion years ago (or at any other time), and so there's ostensibly nothing to explain (ignoring the far more general question of "why is there something instead of nothing?", which as you note arises independently of how you model the history of the universe).

But once you've decided that an eternal universe is "easier" to explain than a universe with a beginning, then when the Big Bang comes along and ruins your nice steady state model, it becomes convenient to try and fold the Big Bang into an eternal universe as a natural event with a natural cause, rather than scrapping the whole idea and starting over with stronger assumptions. I believe this is what at least some philosophers are doing.

Answer 2

Can something come from nothing? If so... what is it... that supposedly came from nothing?

What I mean by that is...

1. What fundamentally exists, now, today?

2. Fundamentally what is reality made of?

3. What fundamentally exists now that supposedly came from nothing?

I suggest there are none that can answer the above questions.

Making claims about beginnings, and the nature of time... premature (before their time), from a knowledge, logic and intellectual perspective.

But I may be wrong. To support my claim... Here is a list of "Candidate Theories of Everything" lifted from Wikipedia, along with a list of "candidate theories of quantum gravity" also from Wikipedia

1. Wikipedia: Theory of Everything

2. Wikipedia: Theory of Quantum Gravity

3. Letter: From Isaac Newton to Richard Bentley

Here is a pictoral summation of some of the groups of types of candidate theoretical fabrics of reality, related by mathematical approach... from Nature Magazine...

4. Poster: Merali, Z. Theoretical physics: The origins of space and time. Nature 500, 516–519 (2013). https://doi.org/10.1038/500516a

And this sums up the situation rather well, I would call it a pragmatist's perspective on current academic physics...

“Aristotle said a bunch of stuff that was wrong. Galileo and Newton fixed things up. Then Einstein broke everything again. Now, we’ve basically got it all worked out, except for small stuff, big stuff, hot stuff, cold stuff, fast stuff, heavy stuff, dark stuff, turbulence, and the concept of time”

― Zach Weinersmith, Science: Abridged Beyond the Point of Usefulness