Disallowing additions of (implicitly int-converted) bool values is a bad idea. A huge advantage of C++ is the long compatibility for low-level algorithms. They can just be inserted and compiled. bool a = true; bool b = true; bool c = false; if (a + b + c >= 2) ...; // test whether at least two booleans are true We should create the std::strong_bool instead or use some bool profile.