This article shows the complexity that characterizes the normative structure of contractual good faith. Even though the law of contracts is usually understood as uniformly grounded on individualism, this is not entirely correct. Good faith conspicuously reveals the dual normative structure of contractual law. This contemplates claims based on a form of individualism, as well as exigencies derived from a certain way of understanding altruism. By breaking down the duties of the contractor in good faith, it is possible to reveal that individualism, not even in its vigorous version, is able to account for them thoroughly. The contractor in good faith must, in certain occasions, act positively in favor of the interest of the other, and an appropriate normative foundation for those requirements must challenge the predominance of personal interest. It is analyzed in what sense good faith answers to individualistic, as well as to altruistic basis. Although it is not necessary for the contractor to really be altruistic, but for her acts as if she were, just as it is the case regarding objective good faith as standard of conduct.