Page:Russell, Whitehead - Principia Mathematica, vol. I, 1910.djvu/139

SECTION A] Note that, in the above proof, "(1)" stands for the proposition as was explained in the proof of *2·31.

$$\scriptstyle{\vdash.\sim(p.\sim p)}$$

Dem.

The above is the law of contradiction.

$$\scriptstyle{\vdash:p.q.\supset.p}$$

Dem.

$$\scriptstyle{\vdash:p.q.\supset.q}$$

Dem.


 * 3·26·27 will both be called the "principle of simplification," like *2·02, from which they are deduced. They will be referred to as "Simp."

$$\scriptstyle{\vdash:.p.q.\supset.r:\supset:p.\supset.q\supset r}$$

Dem.

$$\scriptstyle{\vdash:.p.\supset.q\supset r:\supset:p.q.\supset.r}$$

Dem.