Types of Mistakes in Science and Their Impact on Popper's Notion of Verisimilitude

In this chapter, I will propose a new sense of the notion of verisimilitude that Popper put forward in various essays ( Popper, 1963 , 1972 ). I will use this new sense to detach the notion of epistemic verisimilitude from the notion of truthlikeness. Popper equates the two concepts, but I will argue that this is wrong. We can increase the epistemic verisimilitude of our theories without knowing or caring whether we are increasing their truthlikeness. I will then compare this new notion of verisimilitude with Popper’s and explain why he mistakenly thought that verisimilitude and truthlikeness were the same epistemological property of scientific theories. Popper’s problems stem from the way in which he conceives of the relationship between verisimilitude and truth. To explain why this is so, it is important to distinguish between different kinds of empirical successes and errors and the roles they play over time in the replacement of our scientific theories. A new sense of scientific progress and truth emerges from this historical reflection. I will also explore the implications of my proposal for other realist philosophers of science, including Graham Oddie and Ilka Niiniluoto, who have criticized Popper but have also defended the identification of truthlikeness with verisimilitude.