Why believe in brute facts?
Metaphysical rationalism, which I defend in my book and in this blog, says there’s no such thing as a brute fact ‒ a fact that has no explanation, not merely an explanation we have yet to discover. But suppose we’ve tried hard, without success, to explain some fact, such as the fact that the cosmological constant is vastly smaller than our best-confirmed theories say it should be. Under which circumstances could we rationally conclude that the fact is brute, that it has no explanation at all?
None, so far as I can see. The space of possible explanations is infinite. At any time, we will have explored only a finite part of it. Furthermore, for all we know the unexplored part differs in unimagined ways from the part we’ve explored.
Having discovered the existence of gravity, someone as brilliant as Newton couldn’t explain why gravity exists or why it affects bodies that have no tangible connection between them. Yet he didn’t conclude that those facts have no explanation. A little more than two centuries later, and using methods and data unavailable to Newton, Einstein offered one. For rationalists, of course, Einstein’s explanation can’t be a brute fact either, nor can its explanation, and so on without end.
As I wrote on pp. 158-159 of my book,
an infinitely regressive pattern of explanation fits perfectly the history of scientific discovery so far, in which ever more basic and more general laws have explained phenomena that stumped previously discovered laws ‒ or have explained the phenomena in a simpler, more unified way ‒ while also explaining why those previously discovered laws got right what they did. Every so often physicists succumb to the temptation to declare “The End of Physics” because the dominant theory of the physical laws ‒ whether Aristotle’s, Newton’s, or Maxwell’s ‒ explains so much so well. The history of science counsels us to resist that temptation. The laws go ever deeper.
