Because you can prove once and for all that in any process which behaves like integers, 2 thingies + 2 thingies = 4 thingies.
I expected at this point the mathematician to spell out the connection to the earlier discussion of defining addition abstractly—“for every relation R that works exactly like addition...”
I expected at this point the mathematician to spell out the connection to the earlier discussion of defining addition abstractly—“for every relation R that works exactly like addition...”