Thank you News for pointing us to the Sean Carroll/Luke Barnes exchange. Here are some of highlights:
There was an extremely interesting discussion about whether Carroll’s explanation of the existing of the universe (i.e., it’s a brute fact; we have no explanation) is tenable. Here are the highlights:
Carroll starting at 30:13:
I don’t think that I am especially bothered by the existence of brute facts in a physicalist or naturalist account of a universe with a beginning.
Then Carroll starting at 36:10:
there’s this temptation, there’s this feeling like, you know, there must be explanations for things. And I think that in the context of modern science, modern physics, that’s not the right way to think. I think that we need to think about what you mean by an explanation; there’s different kinds of explanations. When we get into things like the causes of things and so forth, there is a very very different picture we have in modern physics than sort of the folk understanding of explaining why your car died. Well, because it ran out of gas, right? And I think that there’s a different way of thinking about things at the deepest level that has been very very successful to modern science, and in some sense, it’s a much more straightforward simple demand – it’s find the laws of physics, find the patterns that nature seems to obey and ask what things could happen that are consistent with those patterns and what things would not happen that are not consistent with those patterns. The language of causes and explanations is inappropriate when we are talking about the fundamental nature of reality. So . . . from that perspective there is zero bother or worry in my mind that the universe can exist. Things are going to exist. The question is, do things obey the laws of nature?
Then Carroll starting at 38:02:
There’s always the very very real possibility that we don’t understand everything about the universe. Maybe what we see as the universe is part of some much larger framework, whether it’s a multiverse or something even beyond that, and within that framework one can talk about causes. But, uh, if the universe is the whole of physical reality, then talking about causes, looking for causes, would be inappropriate. And I think that it is exactly parallel to the idea of, you know, “could the universe have had a first moment of time.” When I was debating William Lane Craig, he was incredulous that I could imagine both that the universe had a first moment and that it was uncaused, and his argument was basically like “if universes can just pop into existence, then why don’t bicycles pop into existence.” And the point is well we have perfectly good explanations for that: “bicycles popping into existence would violate the laws of physics. It would violate laws of conservation of energy and momentum and things like that.” The question to ask is would a universe having a first moment of time violate the laws of physics? To the best of our current understanding the answer is no.
Barnes calls him on this. First, he confirms Carroll’s view that the laws of nature are merely observed regularities – “patterns” is the word Carroll uses. The word “law” is confusing; the laws of nature do not govern nature in any meaningful sense. They are mere descriptions of what happens. To say that a bicycle popping into existence in London means one and only one thing – a bicycle popping into existence in London has never happened before. It does not mean that it never will. In fact, if a bicycle were to pop into existence on the 10th of October, then “bicycles popping into existence” would from that point be perfectly consistent with the laws of nature in Carroll’s view.
At 40:49 Carroll concedes this point: “Yeah, that’s right and that’s completely plausible if that were what the evidence demanded. Happily, we have a much simpler theory, which is “here the laws of nature and that’s it,” and I think that’s what our burden is as scientists to find the best possible theory to explain what we see in nature. I don’t feel the need to grant the laws of nature any coercive properties. They’re a description of what happened.
Barnes hold’s Carroll’s feet to the fire at 42:05:
Right, but remember the question. The question was . . . if there are brute facts – like the existence of the universe — why aren’t there more brute facts? That was the question. The question was, what, for example, “why don’t bicycles appear in this room right now?” And it sounded like the answer you gave ultimately was, “well thankfully in our universe that doesn’t happen.” But that’s not an explanation. If brute facts are allowed, why aren’t there more of them? . . . the real problem is if you allow brute facts, they don’t have reasons, and so there can’t be a reason why there aren’t more brute facts or less brute facts or only universe is a brute fact rather than bicycles being brute facts. So the objection here is that once you’ve allowed – once you’ve opened the door to brute facts – you can’t then stop, you know, the whole party piling in. It’s a clown car; everything’s going to come flying out. Why aren’t there more brute facts? The fact that there aren’t more brute facts, the fact that there is a simple way of describing a universe in which there are no bicycles that pop into existence, is the thing to be explained.
In response Carroll explicitly gives up on the law of sufficient reason at 43:07:
Yeah, but it may not be an explanation. I don’t think we have a right to demand an explanation for that. I think that the fact that there a very few brute facts is a brute fact.
Then, at 43:47 Carroll makes an astonishing assertion. The moderator keys off Carroll’s statement that we don’t have a right to demand and explanation and asks when do we a right to demand an explanation. Carroll responds:
Well, in the context of some bigger picture, right? So . . . we explain why bicycles don’t pop into existence. Because there’s something called conservation of energy and momentum. And you say, well, why is there conservation of energy and momentum? Well, because the laws of physics have this property that there’s certain symmetries. Why do they have that property? Well, I don’t know. That’s just it. That, that’s the bottom, right. I think that there’s absolutely no way out of hitting a bottom of these chains of explanations.
I find it remarkable that a prominent cosmologist is so incurious and irrational at the same time. The laws of physics and the existence of space-time are just brute facts that cannot be explained. He does not argue that they are in any sense necessary. He just thinks he can get his contingency free. Wow.
At 1:14:36 Carroll takes exactly the same tack to handwave fine turning away:
Why is it that way? And I’m just really happy with saying that eventually we find that that’s the way it is. I’m not gonna rely or be in on the idea that someday we’ll find that’s the only way it could have been. I’m just really happy with – and comfortable with – brute facts. I don’t think that there is any way around that.
I did agree with one of his observations. Carroll starting at 21:50:
There’s this idea called methodological naturalism, which . . . is usually defined as the idea that when science tackles a question, science is only allowed to suggest naturalistic explanations, that the way that science moves forward is by assuming that naturalism is true, whether or not it is true, but what science does is look for the natural explanations. Now I think number one this is false; that’s not actually what science does; I think that science looks for the true explanations. And number two I think that this is a attempt to do something politically savvy, especially here in the United States, but failing even on that score . . . This idea of methodological naturalism as much, as anything else, grew out of the idea that we shouldn’t be teaching creationism in schools. So it was an attempt to define what you teach in science class to preclude supernatural explanations from the start. So I think it was sort of bad politics and bad philosophy at the same time.
Who would have thought that I would be in whole-hearted agreement with a prominent atheist?