"Abstract This is the proposed wording for a unified call syntax based on the idea that f(x,y) can invoke a member function, x.f(y), if there are no f(x,y). The inverse transformation, from x.f(y) to f(x,y) is not proposed." They were considering 6 alternatives and chose the worst... https://isocpp.org/files/papers/P0251R0.pdf