In his book, The Art of Unix Programming, Eric Raymond proposed the Rule of Modularity:
"Developers should build a program out of simple parts connected by well-defined interfaces, so problems are local, and parts of the program can be replaced in the future versions to support new features. This rule aims to save time on debugging complex code that is complex, long, and unreadable."
Large systems are hard to reason about, especially when the boundaries of internal components are fuzzy, and the interactions between them are complex. This principle of building large systems out of small, simple, and loosely-coupled pieces is a good idea for software and beyond. Physical manufacturing, management theory, education, and government, ...
