6.241 So the proof of the proposition 2 x 2 = 4 runs thus:

(^v)^µ'x=^v×µ'x Def.
^2×2'x = (²)²'x = (²)¹⁺¹'x = ²'²'x = ¹⁺¹'¹⁺¹'x
= (')'(')'x = ''''x = ^1+1+1+1'x = ⁴'x.

What’s going on here? I thought there was no proof in mathematics? See 6.2321.

Black (p. 343): “W.’s proposed ‘proof’ is eccentric and would not satisfy contemporary standards of mathematical rigour. It may be pointed out, for instance, that he has provided no rules for the use of variable superscripts with the lamda symbol.”