Research into statically typed functional languages approaches this question, and generates some pretty good insight. It turns out that OO is sort of a religion

Research into statically typed functional languages approaches this question, and generates some pretty good insight. It turns out that OO is sort of a religion... just one approach to modularity and abstraction. Languages like ML and Haskell provide these features in a completely non-OO style, and are very expressive and powerful. If you are curious, look at abstract data types and polymorphism in SML/OCaml and Haskell. Also, look at Haskell's type classes, and look at SML/OCaml's module system. Here's a paper you can read: http://www.cs.utexas.edu/~wcook/papers/OOPvsADT/CookOOPvsADT90.pdf http://www.cs.utexas.edu/~wcook/papers/OOPvsADT/CookOOPvsADT...