Reciprocal altruism and inclusive fitness are generally considered alternative mechanisms by which cooperative, altruistic traits may evolve. Here we demonstrate that very general versions of Hamilton's inclusive fitness rule (developed by Queller) can be applied to traditional reciprocal altruism models such as the iterated prisoner's dilemma. In this way we show that both mechanisms rely fundamentally on the same principle - the positive assortment of helping behaviors. We discuss barriers to this unified view, including phenotype/genotype differences and nonadditive fitness (or utility) functions that are typical of reciprocal altruism models. We then demonstrate how Queller's versions of Hamilton's rule remove these obstacles.