Thank you all for this great discussion!

Here's an initial response to SophistiCat's interesting observation:

Of course, that's one possible explanation. Another is that we expect to find structure, are constrained by our mental constitution to find structure, and that is why we find it. This isn't as neatly self-contained as the first explanation, since it doesn't explain why we are constituted this way and how it is that we exist at all, in contrast to this: — SophistiCat

But what if there is some truth to the second possibility? What if the world is not quite as regular as our science implies, but we are biased against noticing this fact, because we have evolved to seek out and take advantage of regular structures? — SophistiCat

I can think of two arguments against this possibility.

1. Consider just how implausible it would be for the development of structure in the world--any structure, never mind galaxies, solar systems, complex molecules, life, or intelligent life--without regularity. I'm not sure what a non-regular cosmos would be like, but I think it would be very messy and without much ordered complexity. The fact that we do see all of these things means that things had to behave according to some rules, at least most of the time.

And to the extent that there might have been spatially or temporally local sources of irregularity that did not affect the development of overall structure, scientists have had a hard time finding them. When they seem to have found an irregularity, it is then, eventually, subsumed into some more general, and no-less-regular, theory. This leads me to the next argument.

2. On the fundamental level of matter, space, and time, the world has proved to be extremely regular. Our best theories about these fundamental entities (QM and GR) make astoundingly precise predictions, are the basis for new and surprising discoveries about realms extremely removed from our own in scale and distance, and allow for the development of useful technology that might have a few decades ago seemed magical. There is also a very good case to be made that matter space and time are truly fundamental--all phenomena can be in some sense be reduced to considerations about matter moving around in space and time.

So it's hard to see how the world couldn't be as regular as science implies. Surely we animals find regular structures helpful, and so look out for it. But where would this non-regularity fit? It can't be in the behavior of matter, space, and time, because we have very effective (as characterized above) theories that constrain the behavior of those things to a remarkable degree.