• teaching critical thinking;
  • Karl Popper;
  • falsificationist epistemology and methodology;
  • confirmation bias;
  • confirmation and disconfirmation strategies in hypothesis-testing and problem-solving


Based on a rather simple thesis that we can learn from our mistakes, Karl Popper developed a falsificationist epistemology in which knowledge grows through falsifying, or criticizing, our theories. According to him, knowledge, especially scientific knowledge, progresses through conjectures (i.e. tentative solutions to problems) that are controlled by criticism, or attempted refutations (including severely critical tests). As he puts it, ‘Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problem which we are trying to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory ... is always a step forward that takes us nearer to the truth. And this is how we can learn from our mistakes’ (1989, p. vii). Since criticism plays such a crucial role in Popper's falsificationist methodology, it seems natural to envisage his heuristic as a helpful resource for developing critical thinking. However, there is much controversy in the psychological literature over the feasibility and utility of his falsificationism as a heuristic. In this paper, I first consider Popper's falsificationism within the framework of his critical rationalism, elucidating three core and interrelated concepts, viz. fallibilism, criticism, and verisimilitude. Then I argue that the implementation of Popper's falsificationism means exposing to criticism various philosophical presuppositions that work against criticism, such as essentialism, instrumentalism, and conventionalism; it also means combating what seems a common tendency of humans to be biased towards confirmation. I examine the confirmation bias, to which Popper did not give much attention: its pervasiveness and various guises, some theoretical explanations for it, and the role of teachers in undermining its strength and spread. Finally, I consider the question whether students can and should be taught to use disconfirmatory strategies for solving problems.