Rudolf Carnap was born on May 18, 1891, and Hans Reichenbach on September 26 in the same year. They are two of the greatest philosophers of this century, and they are eminent representatives of what is perhaps the most powerful contemporary philosophical movement. Moreover, they founded the journal Erkenntnis. This is ample reason for presenting, on behalf of Erkenntnis, a collection of essays in honor of them and their philosophical work. I am less sure, however, whether it is a good time for resuming their philosophical impact; their work still is rather part than historical basis of the...

It is an obvious fact that human agency is constrained and structured by many kinds of rules: rules that are constitutive for communication, morality, persons, and society, and juridical rules. So the question is: what roles are played by social rules and the structural traits of human agency in rational decision making? What bearing does this have on the theory of practical rationality? These issues can only be discussed within an interdisciplinary setting, with researchers drawn from philosophy, decision theory and the economic and social sciences. The problem is of profound, fundamental...

In this collection I present 16 of my, I feel, more substantial papers on theoretical philosophy, 12 as originally published, one co-authored with Ulrike Haas-Spohn (Chapter14), one (Chapter 15) that was a brief conference commentary, but is in fact a suitable appendix to Chapter 14, one as a translation of a German paper (Chapter 12), and one newly written for this volume (Chapter 16), which, however, is only my recent attempt to properly and completely express an argument I had given in two earlier papers. I gratefully acknowledge permission of reprint from the relevant publishers at the...

Wolfgang Spohn presents the first full account of the dynamic laws of belief, by means of ranking theory. This book is his long-awaited presentation of ranking theory and its ramifications. He motivates and introduces the basic notion of a ranking function, which recognises degrees of belief and at the same time accounts for belief simpliciter. He provides a measurement theory for ranking functions, accounts for auto-epistemology in ranking-theoretic terms, and explicates the basic notion of a (deductive or non-deductive) reason. The rich philosophical applications of Spohn's theory include:...