The Architecture Of Complexity — Herbert A. Simon
www.cs.brandeis.edu/~cs146a/handouts/papers/simon-complexity.pdf
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Thus, the central theme that runs through my remarks is that complexity frequently takes the form of hierarchy, and that hierarchic systems have some common properties that are independ- ent of their specific content. Hierarchy, I shall argue, is one of the central structural schemes that the architect of complexity uses.