> Distinguishing mutability has its advantages I think it's misleading to say that Rust distinguishes mutability. It distinguishes _exclusivity_. If you hold a

> Distinguishing mutability has its advantages I think it's misleading to say that Rust distinguishes mutability. It distinguishes _exclusivity_. If you hold a reference to something, you are guaranteed that nothing else holds an exclusive reference to it (which is spelled &mut). You are _not_ guaranteed that nothing accessible through that reference can change (for example, it might contain a RefCell or other interior-mutable type). Shared references (spelled &) usually imply immutability, but not always. On the other hand, if you hold an exclusive reference to something, you are guaranteed that nothing, anywhere, holds any kind of reference to it. IMO, the fact that exclusive references are spelled "&mut", and often colloquially called "mutable references", was a pedagogical mistake that we're unfortunately now stuck with.