(third Earl Russell) (1872–1970), wrote voluminously on philosophy, logic, education, economics, and politics, and throughout his life was the champion of advanced political and social causes. While much of his writing was relatively practical and ephemeral in intent, he also contributed work of lasting importance in some of the most technical fields of philosophy and logic. He was the inventor of the Theory of Descriptions. The Principles of Mathematics (1903) and Principia Mathematica (the latter in collaboration with A. N. Whitehead, 1910) quickly became classics of mathematical logic. Other important philosophical works include The Analysis of Mind (1921), An Inquiry into Meaning and Truth (1940), and Human Knowledge, Its Scope and Limits (1948). Russell was awarded the Nobel Prize for literature in 1950.