The title of

Bertrand Russell and

Alfred North Whitehead's mammoth

1912 attempt to bring all

arithmetic under a

formal axiom system.

One curious aspect of

*Principia Mathematica* is that it does not prove

**1 + 1 = 2** until page 362.

The name

*Principia Mathematica* is also used to refer to Sir

Isaac Newton's landmark work

*Principia Mathematica Philosophiae Naturalis*.