Adjunct Professor of Physics at Northeastern University in Boston, Graham Farmelo, on Paul Dirac and the Religion of Mathematical Beauty. Apart from Einstein, Paul Dirac was probably the greatest theoretical physicist of the 20th century. Dirac, co-inventor of quantum mechanics, is now best known for conceiving of anti-matter and also for his deeply eccentric behavior. For him, the most important attribute of a fundamental theory was its mathematical beauty, an idea that he said was "almost a religion" to him.