Q: Alan, how do you suggest coding? Alan: well we should not have one big source of data. We should organize code into compartments each doing it's own thing with their own data like cells. Q: How would that work Alan: Message passing!

Few years later Q: What is OOP? Inheritance, polymorphism, etc? Alan: It is message passing. All the other stuff I haven't figured it out yet. They are just nice to have things.

Me: Actually OOP is code organized into cell/computer like structure that happen to use messages to make it work.

Dear Alan don't emphasize message passing although that is a way to deny the other techniques as non-essential to OOP.