This article argues that inquirers should adopt an active orientation to the limits of their knowledge, an approach referred to as “Transformational Fallibilism”. Drawing on the Popperian tradition, this approach treats the fallibility of knowledge as more than a philosophical nicety, rather seeing the questioning of claims, including those that have been successful, as a key way to improve the understandings of inquirers. This is illustrated with reference to the example of Newtonian and Einsteinian understandings of gravity and time in (...) the natural sciences, and debates about the role of fathers in child-rearing in the social sciences. I compare this approach to that found within critical realism, arguing that while defenders of the latter acknowledge fallibility to some extent, certain of their arguments also place problematic limits on it. Examining Sayer’s work, I argue that his view that practically successful understandings reveal something about the structure of the world involves an overconfidence in these understandings. I suggest that Elder-Vass’s use of the idea of approximate truth involves a similar difficulty. By contrast, I argue for the importance of treating all elements of the understanding, including those bound up with practical successes, as potentially in need of reconstruction at any point. (shrink)