Protagoreanism, the contention that whatever is affirmed is both true and false, and incommensurability, the contention that there is no common conceptual ground for adjudicating competing claims, undermine realism, the belief that we can learn truths about what we take to be the real world. Margolis wants to retain both realism and a third sort of relativism, which he believes avoids the errors of the other two. In his view, judgments that would standardly count as contradictories are not incompatible because logically weaker truth-values are applied to them by relativizing them to evidence at a given time. Margolis ties this relativism to methodological and substantive considerations about the world we investigate.