I asked What are numbers? Numbers are numbers of something(s). The answer to 1 + 1 = ? depends on what those 1s are. 1 (apple) + 1 (apple) = 2 (apples) 1 (Girl) + 1 (Boy) = 1 (couple :-) 1 (liter) + 1 (meter) = cardinal sin (pun intended ;-)