Kay's ideas are about building complex systems from isolated components ("cells") which may evolve independently. The web is an example: there's a server and a

Kay's ideas are about building complex systems from isolated components ("cells") which may evolve independently. The web is an example: there's a server and a page and a browser and the user's extensions, all changing without reference to each other. How can they all work together? Answer: keep them isolated (no direct function calls), defer most choices to runtime, make it easy to interrogate each others' interfaces. I think that sums up OO. "Call this function if it exists at runtime" is trivial in JS, but a crisis in Haskell. You may not need that stuff. If you're statically compiling your code and all dependencies, it seems pointless. But if you're building a system which talks to code not under your control, code you cannot just refactor at will, then I don't know of any better techniques than OO.