Some optimistic folks hope that Science will eventually explain everything about the world. But this hope seems absurd in light of the fact that explanations always involve presuppositions. The structure of explanation is always that we explain one thing A in terms of some set of other things B, C, D... which exist, or which have happened. (Let's not be too particular about what we mean by “things” here, whether “objects”, “events” or what...) One could then ask what is the explanation of B or C or D, and these things will in turn typically have explanations in terms of other things. This gives us various types of explanatory series, and we can ask whether these terminate in some type of ultimate explanation.
So it seems that the best we could possibly do is to have one thing or principle whose existence is unexplained, and then use that to explain everything else. That one thing would then have no other explanation outside of itself. However, we can still evaluate how plausible it is that it should exist, based on various considerations of parsimony. We can ask:
- Is this entity the type of thing where it would make sense for it to just exist on its own? Or is it the sort of thing that would more naturally be explained by reference to something else?
- Is this the simplest conception of fundamental reality, or can we get away with a simpler one? (Here I am using simple in the sense of Occam's razor, although if there were really just one unexplained entity, not composed of parts, it would also be simple in the Medieval Scholastic sense of being non-composite.)
You might notice that the people of a scientific bent tend to focus exclusively on the second question, while traditional metaphysics focuses more on the first question. In my view both questions are relevant.
I said that explaining everything in terms of one thing is the best we can do. We might have to settle for less, such as a plurality (hopefully small) of unexplained fundamental principles. However, that would not only be more complicated, it would also raise questions about what is it that joins these (supposedly separate) principles together. We might therefore reasonably hope that the principles in question would at least have some type of internal unity, without being too dogmatic at this stage about what kind of unity we are looking for.
Some people might propose that the chain of explanations extends backwards forever in an infinite chain. Thus nothing has any ultimate explanation, but rather each one is explained by the thing before it, and so on. Alternatively one could have the explanations arranged in a circle, which is similar to the infinite regress for what I am about to say.
The chain of explanations wouldn't necessarily have to be embedded in any kind of temporal sequence, but if it were, one would have to have a universe which is eternal to the past. Now there are physics problems with trying to make a compelling physical model along these lines, with neither a geometrical nor a thermodynamic type of beginning. But here I'm trying to explore more general metaphysical considerations, of the sort that are accessible from the nearest armchair, so I'll try to appeal to intuition instead of esoteric quantum cosmology considerations, for which the evidence of a beginning is mixed.
Personally, I find an infinite regress, with nothing more behind it, rather unsatisfactory. It is not that I think there is any logical inconsistency in a universe which extends backwards in time forever. There isn't. The universe might well work that way. But I feel like such a chain of explanations wouldn't actually explain anything in the chain properly. For example, in the “ekpyrotic” scenario where the universe involves an eternal bouncing back and forth of two membranes, it wouldn't tell us why there are two membranes rather than one or four. It would just boil down to saying that: things just are the way they are because they are the way they are. Of course, if there were some additional extra explanation outside of time which somehow determined that there had to be two membranes, that would be different, and would make me much more satisfied with a time that goes back forever.
Somebody might retort that explaining everything in terms of one unexplained thing is just as bad in that it also has something which “just is the way it is”. But at least in that case it there's only one thing like that, not a whole chain of things. I find in myself an intellectual preference for building explanations on a foundation. Axiomatic reasoning is usually regarded as more intellectually respectable than circular reasoning. If we deduce things from axioms, those axioms can be appreciated and evaluated. Whereas if we deduce things from a chain going back to infinity, I feel that the entire system is unsupported in a vicious way. So I'm fine with time going back to infinity, but only if there is something which transcends time which makes time do that. Of course, Nature does not necessarily have to correspond to my intuitions, but I don't think it's irrational to believe that at least some of our intuitions give us rational guidance about how the universe should work. Without some rational intuitions leading us to seek explanations, Science couldn't even get off the ground.
Furthermore, there are chains of explanation which do not go further and further back into the past, and these chains cannot be accounted for simply by postulating an infinite past. We might also try to explain why the present-day dynamical processes of nature occur in the way that they do. For example, suppose I want to know why a balloon attracts hair. So I say it is because they have opposite electrical charges, which are attracted to each other with an inverse square law. Well, why is that? Well, because each charge has electric field lines coming out of it. Why is that? Because Gauss's equation said it had to happen that way. Why is that? It seems the answer must eventually be: it happens by MAGIC.
Some would say that this is obscurantism and that things happen because of the Laws of Nature. But we have to remember that the phrase “Laws of Nature” is really a stand-in for whatever mysterious aspect of reality causes things to obey these Laws of Nature. When the phrase was first coined, the word “law” was a metaphor which was taken to imply the presence of a Legislator. St. Chesterton suggests that the rational agnostic should instead use a different type of terminology, borrowed from fairy tales:
In fairyland we avoid the word "law"; but in the land of science they are singularly fond of it. Thus they will call some interesting conjecture about how forgotten folks pronounced the alphabet, Grimm's Law. But Grimm's Law is far less intellectual than Grimm's Fairy Tales. The tales are, at any rate, certainly tales; while the law is not a law. A law implies that we know the nature of the generalization and enactment; not merely that we have noticed some of the effects. If there is a law that pick-pockets shall go to prison, it implies that there is an imaginable mental connection between the idea of prison and the idea of picking pockets. And we know what the idea is. We can say why we take liberty from a man who takes liberties. But we cannot say why an egg can turn into a chicken any more than we can say why a bear could turn into a fairy prince. As ideas, the egg and the chicken are further off from each other than the bear and the prince; for no egg in itself suggests a chicken, whereas some princes do suggest bears. Granted, then, that certain transformations do happen, it is essential that we should regard them in the philosophic manner of fairy tales, not in the unphilosophic manner of science and the "Laws of Nature." When we are asked why eggs turn to birds or fruits fall in autumn, we must answer exactly as the fairy godmother would answer if Cinderella asked her why mice turned to horses or her clothes fell from her at twelve o'clock. We must answer that it is magic. It is not a "law," for we do not understand its general formula. It is not a necessity, for though we can count on it happening practically, we have no right to say that it must always happen. It is no argument for unalterable law (as Huxley fancied) that we count on the ordinary course of things. We do not count on it; we bet on it. We risk the remote possibility of a miracle as we do that of a poisoned pancake or a world-destroying comet. We leave it out of account, not because it is a miracle, and therefore an impossibility, but because it is a miracle, and therefore an exception. All the terms used in the science books, "law," "necessity," "order," "tendency," and so on, are really unintellectual, because they assume an inner synthesis, which we do not possess. The only words that ever satisfied me as describing Nature are the terms used in the fairy books, "charm," "spell," "enchantment." They express the arbitrariness of the fact and its mystery. A tree grows fruit because it is a magic tree. Water runs downhill because it is bewitched. The sun shines because it is bewitched.
I deny altogether that this is fantastic or even mystical. We may have some mysticism later on; but this fairy-tale language about things is simply rational and agnostic. It is the only way I can express in words my clear and definite perception that one thing is quite distinct from another; that there is no logical connection between flying and laying eggs. It is the man who talks about "a law" that he has never seen who is the mystic.
(Orthodoxy, "The Ethics of Elfland").
Let no one think that St. Chesterton said this only because he did not understand the particular explanations given by Modern Science. He didn't, but it doesn't make any difference, since you come to the same place in the end no matter what. No matter how many mediators we put in between the hair and the balloon—even if there is a continuum of mediating entities—at some point we need to postulate some sort of fundamental interaction not explained through intermediaries.
If we ask why these direct interactions occur, we either have to say for no reason at all (in which case it is a puzzle why things happen so consistently, since every single instance of an interaction would be a quite separate unexplained occurrence) or else to say that there is some common force or principle: either God or else some other term more acceptable to atheists. We can call the underlying principle a “Law” if we want to (for lack of better language) but we should be aware that the word doesn't really explain why things had to be this way.
So in what follows, let's suppose that the explanations terminate on one or more unexplained entities, whether laws of physics, divinities or something else. Because of the uncertainty about what these things actually are, I am not going to impose a rigid grammar on them, but will freely alternative between different terms. I don't mean to sneak in any substantive assumptions by calling them “things”, “entities”, “principles”, “rules”, “beings”, or whatever.
Still, they must in some sense exist, or they couldn't do any work explaining anything else. They are not merely logical abstractions, since logical abstractions can't do anything, they can only describe things. Some people would say that it's a category error to say that laws can do anything, that laws merely describe regularities in Nature, but don't cause them to exist. Well, if that happens to be true, then (contra Hume) something else must cause those regularities to keep occurring, otherwise it would just be a mighty coincidence that the regularities keep on happening.
In the following reflections I will try to say more about what this “something” might be. I'm not trying to force a prematurely theological conclusion here. I'm reasonably confident that any rational, complete worldview must have some set of fundamental entities or explanations which play the explanatory role that God does in Theism, but it is a quite separate question whether the thing(s) that fill that role have to be at all like the traditional conception of God. This is a question which we will eventually need to face square-on, but first let's try to figure out some properties that any fundamental entities would have to have, no matter whether they are conceived of along Naturalist or Supernaturalist lines.