Your last sentence there is pretty unnecessary. Moving along... Echoing my sibling comment: immutability is a defining feature of FP, so there is no way to pu

Your last sentence there is pretty unnecessary. Moving along... Echoing my sibling comment: immutability is a defining feature of FP, so there is no way to put it aside if we're talking about FP. As for the rest of your argument, I'm a bit of meathead and maybe haven't followed it fully. My thought is that in OO, an instance of an object can be passed some data that it processes along with its own internal state. If that data is a reference to another object, then that object could be changed while the receiving object is doing its thing. The receiver then would go and store its results within itself. In functional, functions receive everything as parameters and all that data is guaranteed not to change for duration that the function runs. Once it returns, it will update the global state and then, again as my sibling comment points out, it's far easier to check validity of the whole shebang as it's in one place. As for "you have a lot less code to look through", I feel this is a common thing said by folks who have not really grokked how FP works. I say this because I used to make this argument ;P While FP can be slightly more verbose than OO, I've found FP way easier to figure out where things came from. All in all, I don't have a vendetta against OO. I was really just trying to get across that I was a big OO enthusiast and went in FP perhaps even with a closed mind and it didn't take much to win me over. Having said that, I'm in the Elixir/Erlang world, which is a bit of its own beast. (Edit: your/you’re/yore)