What you're used to seeing might be better described as "class-oriented programming", i.e. Java's take on OOP. Once you realize that `this` is just an implicit

What you're used to seeing might be better described as "class-oriented programming", i.e. Java's take on OOP. Once you realize that `this` is just an implicit parameter and objects are just closures (look at Javascript's OOP for a good illustration of this principle), and you start to think about how objects can interact reliably across interfaces/languages/networks/failures, you more-or-less inevitably end up at "message-oriented programming", i.e. Smalltalk's take on OOP, wrapped up in declarative/functional APIs. Disclaimer: these ideas are all unoriginal and some of them directly borrowed from other commenters in this thread.