Mathematics

Normal          1 + 1 = 2        1 + 1 + 1 = 3      1 + 1 + xy =  xy
Philosophiy    1 + 1 = 3        1 + 1 + 1 = 5      1 + 1 + xy =  ?
Church          1 + 1 = 1        1 + 1 + 1 = 1      1 + 1 + xy =  1