As an aside, 2+2 isn't that hard to explain. "2" is just our name for 1 + 1. So 2 + 2 is 2 + (1 + 1). By associativity of addition, this is (2 + 1) + 1 or ((1 + 1) + 1) + 1. And "4" is just our name for that last value.