This monograph is unique in its kind, giving as it does an independent and self-contained introduction to the eight prominent verisimilitude proposals that make up the verisimilitude literature after the breakdown of Popper's definition in 1974. The author brings them together by comparing the ways in which they order propositional formulae. Using this method, he shows that the distinction of content and likeness definitions partitions the entire field of investigation. In addition, it is shown that the weak content definitions can be strengthened by incorporating considerations of similarity between possible worlds. The resulting refined verisimilitude definition has many desirable properties. For instance, it is the first qualitative proposal that evades the problem of truth-value dependence. In addition, in chapter five the often discussed and misunderstood problem of "language dependency" is solved. The book will be of interest to those working in the fields of logic, epistemology, philosophy of science, and (computational) linguistics.

The subject of the present inquiry is the approach-to-the-truth research, which started with the publication of Sir Karl Popper's Conjectures and Refutations. In the decade before this publication, Popper fiercely attacked the ideas of Rudolf Carnap about confirmation and induction; and ten years later, in the famous tenth chapter of Conjectures he introduced his own ideas about scientific progress and verisimilitude (cf. the quotation on page 6). Abhorring inductivism for its apprecia tion of logical weakness rather than strength, Popper tried to show that fallibilism could serve the purpose of approach to the truth. To substantiate this idea he formalized the common sense intuition about preferences, that is: B is to be preferred to A if B has more advantages andfewer drawbacks than A. In 1974, however, David Millerand Pavel Tichy proved that Popper's formal explication could not be used to compare false theories. Subsequently, many researchers proposed alternatives or tried to improve Popper's original definition."