This paper deals with Popper's little-known work on deductive logic, published between 1947 and 1949. According to his theory of deductive inference, the meaning of logical signs is determined by certain rules derived from ?inferential definitions? of those signs. Although strong arguments have been presented against Popper's claims (e.g. by Curry, Kleene, Lejewski and McKinsey), his theory can be reconstructed when it is viewed primarily as an attempt to demarcate logical from non-logical constants rather than as a semantic foundation for (...) logic. A criterion of logicality is obtained which is based on conjunction, implication and universal quantification as fundamental logical operations. (shrink)

From the time of its birth, Popper’s theory of falsifiability has been fiercely criticized from various viewpoints. In the author’s view, however, those various criticisms all have the same root in their assumption that a falsification must be certain and conclusive. As the theory of falsifiability has never had such an assumption, it is the source of misunderstanding. By discarding it, we can reply to every criticism and thereby clarify the role of falsifiability in our search for better knowledge; that (...) is, it makes our attitude open to a yet unknown world. Key Words: Popper • falsifiability • openness • inconclusive falsification • second Popper legend. (shrink)

Currently, testimony is studied extensively in Anglo-American philosophy. However, most of this work is done from a justificationist perspective in which philosophers try to justify our reliance on testimony in some way. I agree with Popper that justificationism is radically mistaken. Thus, I construct an account of how we respond to testimony that in no way attempts to justify our reliance on it. This account is not a straightforward exegesis of Popper, as he never tackled testimony systematically. It makes use, (...) however, of several of Popper's key insights and incorporates them into a viable theory of testimony. Key Words: testimony • anti-justificationism • social epistemology • situational analysis • defeasibility. (shrink)

Bartley’s pancritical rationalism is seen by some as being a refinement of Popper’s critical rationalism. I contest this view and argue that pancritical rationalism is obtained from critical rationalism by removing some of its most important and useful features. The remainder consists of a restatement of some of Popper’s key ideas and an interpretation of others that I attempt to show is not entirely faithful to what Popper says.