Many theorists have regarded genealogy as an important technique for social criticism. But it has been unclear how genealogy can go beyond the accomplishments of other, more mundane, critical methods. I propose a new approach to understanding the critical potential of history. I argue that theorists have been misled by the assumption that if a claim is deserving of criticism, it is because the claim is false. Turning to the criticism of concepts rather than criticism of claims, I expand on the distinction between “descriptive semantics” and “foundational semantics” to show that genealogy can be uniquely qualified to explore the foundations of concepts, and hence to criticize concepts that are problematic in nonobvious ways. Suppose a critic is concerned about some social phenomenon. She is disconcerted, say, by rehabilitation practices in Texas prisons, or by the aggressive entrepreneurial culture of Silicon Valley, or by the admiration of contestants in “America’s Top Model” for Tyra Banks even as she belittles them. The critic suspects that such phenomena are oppressive, whether or not that oppression is evident to the players involved. To unearth potential oppression, suppose the critic looks into the history of the phenomena in question. For example, she might examine the evolution of approaches to prisoner rehabilitation, testing the hypothesis that actual rehabilitation practices were developed on the basis of public relations value rather than for the good of the prisoners. In showing that the origin of the practice was dubious or deplorable, the critic aims to vindicate her suspicion and undermine the practice, with its history providing an argument for its revision.