 In philosophy of mind, Lewis developed and defended at length a new version of materialism (see the entry on  physicalism).  He started by showing how the motivations driving the identity theory of mind and  functionalism  could be reconciled in his theory of mind. He called this an identity theory, though his theory motivated the position now known as  analytic functionalism.  And he developed detailed accounts of mental content (building on Davidson’s  interpretationism)  and phenomenal knowledge (building on Nemirow’s  ability hypothesis)  that are consistent with his materialism. The synthesis Lewis ended up with is one of the central positions in contemporary debates in philosophy of mind.