As Lewis formulates it, the challenge of radical interpretation is the challenge of specifying how the totality of facts about a subject qua physical system determine that subject's beliefs, desires, and meanings. Lewis proposes six constraints for any proposed solution to the problem of radical interpretation; included among these constraints are the principles of charity (i.e., a subject should be represented as believing and desiring what he or she ought to believe and desire), rationalization (i.e., subjects should be represented as rational agents), and truthfulness (i.e., subjects should be interpreted as operating within a convention of truthfulness). Invoking these constraints, Lewis then considers several methods (one of which he advocates) for solving the problem of radical interpretation. Notably, the Davidsonian method is found to be inadequate because it flouts the principles of truthfulness and rationalization.
Keywords: charity, Davidson, propositional attitudes, Quine, radical interpretation, rationality