In object-oriented languages like Ruby, people often say that “everything is an object”—but first-class functions have become standard for object-oriented languages too. C# has had them and other related features for years, and even Java is in the game these days! Some “functional” languages seem to have some very object-oriented-looking features, too. If that sounds wrong to you, let's talk about polymorphism and more in languages like Clojure, Elixir, and even Haskell! So where does object-oriented programming (OOP) end and functional programming (FP) begin? In this session, you’ll learn to look at these programming paradigms with a more critical eye, focusing on where FP and OOP folks fundamentally disagree, where these paradigms have more in common than the industry's rhetoric suggests, and how you can use those insights to make better decisions about the software you build.