Principia Mathematica

 was a book on mathematics by Bertrand Russell. Nyssa looked over a copy of Principia Mathematica while waiting for the Fifth Doctor to return to the TARDIS. Adric suggested that Tegan should read it, calling it a "fascinating book". (TV: Four to Doomsday)

Behind the scenes
Bertrand Russell and Alfred North Whitehead wrote Principia Mathematica as a three volume work, attempting to show that mathematics could be deduced from a minimized set of axioms and inference rules, solving paradoxes that had at that time been plaguing the foundations of mathematics, using a specific mathematical theory of. A fourth volume was planned to be written by Whitehead on geometry, as well as rebuttals to criticisms, however, Kurt Gödel published his first and second incompleteness theorems in his 1931 paper On Formally Undecidable Propositions in Principia Mathematica and Related Systems I, which spelled the end for this project.