We see levels in the natural sciences all the time.
Mendeleyev figured out the table of organization of
the elements without really understanding any of
the quantum mechanics of electron orbits. You can
study the electron orbits without really understanding
what's going on in the nucleus, and so forth. This
is a familiar kind of thing to us, and one of the things
that the arbitrariness of symbol buys you is this ability
to play the same games with abstractions that you're
playing with concrete objects.
You also see a pyramiding of levels. As babies
encounter the patterns in the world around them, you
get at least four levels. Babies first pick up the short
sound units called phonemes, and once they've found
the common ones in their experience, they form categories
around them. Then they start acquiring the
patterns of phonemes called words at a very substantial
rate just by hearing them. Then they tune up to
the patterns within strings of words - these things
that span many seconds - and the regularities in it
with things that we call syntax. Then they go on to
this fourth stage where they are pattern-finding over
many minutes - these things that we call a good story
or a proper narrative. So, there are four levels in four
years, the pyramiding of taking, in effect, the categories
made at an earlier level and looking for patterns
and how they assemble.