Philosopher, logician, mathematician, social reformer and historian, the renowned Nobel Prize winner Bertrand Russell has been an intellectual force of the twentieth-century, his influence on contemporary thought far reaching. The Analysis of Mind is his attempt to "harmonize two different tendencies, one in psychology, the other in physics ... On the one hand, many psychologists, especially those of the behaviourist school, tend to adopt what is essentially a materialistic position ... They make psychology increasingly dependent on physiology and external observation, and tend to think of matter as something much more solid and indubitable than mind. Meanwhile the physicists, especially Einstein and other exponents of the theory of relativity, have been making 'matter' less and less material."