By the 1960s many, perhaps most, philosophers had adopted 'physicalism' – the view that physical causes fully account for mental activities. However, controversy persists about what counts as 'physical causes'. 'Reductive' physicalists recognize only microphysical (elementary-particle-level) causality. Many, perhaps most, physicalists are 'non-reductive' – they hold that entities considered by other 'special' sciences have causal powers. Philosophy of chemistry can help resolve main issues in philosophy of mind in three ways: developing an extended mereology applicable to chemical combination; testing whether (...) 'singularities' prevent reduction of chemistry to microphysics; and demonstrating 'downward causation' in complex networks of chemical reactions. (shrink)