Principia mathematica, by Alfred North Whitehead ... and Bertrand Russell.

SECTION B]

DESCRIPTIONS

185

Dent.
I-. *10-1. )F:. Hp. ) cb.=. b =b:Ob.=. bc:
[*13-15]:b:b.=.b=c
[Ass] ): b =c:.)-F. Prop
*14'122. F:.4x-v=,x-x=b:=:4x.)z.-x=b:Sbb:
Ox.., = b: (axw). Ox
Dem.
F. *471. )F:.cfx.).x=b:D:.fx.n-.fr.x=b:.
[*10-281] a)-O ax.O.X=b
[*13-195] ob(2)
F. (1). (3).:)F. Prop
The two following propositions (*14-123-124) are placed here because of
the analogy with *14-122, but they are not use(] until we come to the theory
of couples (*55 and *5 6).
*14-123.:.0(z~iv.-Z (z,=w)..z = w=Y(x )
fO(z, w)..z wo= x w= y (az-,w). 4(z, w)
Dem.
(z, w). D z = X. W =: yz = X. *W = Y. (z, w):
F*4-71. )F:.(z, w).)D. z X. w= Y:
D k (z, w). * (z, w). z = X. *w = Y:
): 0 (z, w). z w (z, W).z = X. w =Y
[*112341] (1,W.0(,W 2Z ).9 z ).ZX
[*13-22] u~.(~)(2)
F.(2). *5-32.) F:.q(z, w). *z = x * w =y: (ajz, w). 4(z, w):
F.-(1).(3). DF.Prop