Firstly, "object" as a term is really hard to stick a pin in. It's slippery and hard to talk about, so I'm kind of trying to avoid it. Secondly, "objects" can

Firstly, "object" as a term is really hard to stick a pin in. It's slippery and hard to talk about, so I'm kind of trying to avoid it. Secondly, "objects" can imply open-recursion which can be used to implement inheritance. That said, inheritance isn't the only thing open recursion is good for and inheritance can be implemented without open recursion. "Object"s can also imply codata like structures as compared to data like structures. The distinction is blurry to the point of indistinguishability in essentially all languages, but it's important in theorem proving and math and thus shows up in dependently typed languages. Thirdly, dynamic dispatch is one way to achieve open recursion but it's not the only way. I don't know if dynamic dispatch is useful for things other than open recursion, so offhand I would say "dynamic dispatch => open recursion is being used" but not the other way around. Clojure's multimethod system, given that it's an implementation of dynamic dispatch, implies open recursion and thus has at least one factor which some people associate with objects. It's immutable (at least to the degree which Clojure is immutable) so I'm willing to call it an "immutable object system", yes. But with all of the caveats I just listed!