He asserted the importance of tracing local matters of particular fact, a metaphysical doctrine that he called "Humean supervenience," and employed techniques from game-theory to describe norms as resulting from coordination problems in his first work, Convention.  
With Michael Smith and Mark Johnston he advanced a meta-ethical theory holding that something is valued if, and only if, we would be disposed to value it under ideal circumstances.  He explored what it meant to introduce a new theoretical term into science in such papers as "Tensing the Copula" and "Void and Object."  This process, called Ramseyfication, was also employed in his, "An Argument for Identity Theory," to make a case for mind-brain monism.  He asserted the importance of tracing local matters of particular fact, a metaphysical doctrine that he called "Humean supervenience," and employed techniques from game-theory to describe norms as resulting from coordination problems in his first work, Convention.  Best known for championing modal realism, For 10 points, identify this philosopher who wrote On the Plurality of Worlds.
With Michael Smith and Mark Johnston he advanced a meta-ethical theory holding that something is valued if, and only if, we would be disposed to value it under ideal circumstances.  
David Lewis