What is the contribution of bertrand Russell in mathematics?

Answer 1

Bertrand Russell coauthored a book in the early 20th Century, called Principia Mathematica, in which he tried to show that all mathematical theorems could be derived from a well-defined set of axioms. The only tools to be used were those of logic.

Unfortunately, in 1931, Godel proved that it was an impossible ambition except in very trivial cases. Using any axiomatic system you could find statements that could not be proven to be true or false from within that system.