Traditionally, materialism was a doctrine stating that whatever occurs is reducible to movements of expanded material objects, the latter being defined by spatial properties. Thus conceived, materialism is untenable in terms of modern physics. Its continuation is the belief that all events are really physical, and the question whether mental processes (feelings, thoughts, impressions) can be thus interpreted and whether some realities (e.g. mathematical objects, musical creations) have a separate kind of existence, has been discussed for centuries. Often a person who cares only for material goods is called a ‘materialist’ — Professor Leszek Kołakowski