Evidential support and undermining: Revision of håkan törnebohm's theory of confirmation [Book Review]

In 1975, 'An Essay on Knowledge Formation' by H. Törnebohm was published in this Journal. Its content in revised form was included in a work in Swedish of 1983 on knowledge development. HT defines his confirmation criterion in terms of a measure of truth degree T, which is based on a measure of matching M, which is also used as a measure of the degree to which proposition p (an hypothesis) is supported or undermined by another proposition q (the evidence for p), M is defined in terms of a measure of the content C. Here it is argued that HT works with two measures C: (1) a first C, which is defined only for consistent propositions and which really is a measure of content; (2) a final C, which is an inverted measure of probability rather than a measure of content. As an extension of HT's first C, a new content measure, defined also for inconsistent propositions, is constructed. HT's measure M, which is based on his final C, is replaced by one measure of support and one of undermining. Both are based on the new content measure