Abstract

The notion of truthlikeness, coined by Karl Popper, has very much fallen into oblivion, but the paper defends it. It can be regarded in two different ways. Either as a notion that is meaningful only if some formal measure of degree of truthlikeness can be constructed; or as a merely non-formal comparative notion that nonetheless has important functions to fulfill. It is the latter notion that is defended; it is claimed that such a notion is needed for both a reasonable backward-looking and a reasonable forward-looking view of science. On the one hand, it is needed in order to make sense of the history of science as containing a development; on the other, it is needed in order to understand present-day sciences as containing knowledge-seeking activities. The defense of truthlikeness requires also a defense of two other notions: quasi-comparisons and regulative ideas, which is supplied in this paper as well.