Desiderius Erasmus was really important for starting studies about Greek and Latin at the University. In economics, John Maynard Keynes, Thomas Robert Malthus and Milton Friedman all started their theories in Cambridge. Known philosophers are Bertrand Russell, Ludwig Wittgenstein, George Santayana, Karl Popper and Muhammad Iqbal. Many Archbishops of Canterbury also studied at Cambridge, like Rowan Williams. William Wilberforce helped to stop the slave trade. Thomas Cranmer was an Archbishop who was then killed because of his ideas.