The thing is that that doesn't really match the calling syntax, it matches the syntactic sugar for the calling syntax. Whenever you do thing_instance.foo(b

The thing is that that doesn't really match the calling syntax, it matches the syntactic sugar for the calling syntax. Whenever you do thing_instance.foo(bar, baz) you're secretly calling Thing.foo(thing_instance, bar, baz) Which succinctly explains where the self argument comes from.