Rudolf Carnap’s The Logical Structure of the World

Abstract

Philosophy is facing a serious crisis, but no one cares. When German Idealism, Existentialism, and Marxism allied with Sociology, Psychoanalysis, Cultural History, and Literature Studies in the early 20th century, all attempts at conducting philosophy in a style similar to that of the scientists got expelled from the High Church of Philosophy. The creation of the Wykeham Professorship in Hermeneutics (formerly: Logic) at Oxford and the Stanford Chair of Textual NonPresence (formerly: Methodology of Science) are wellknown indicators of these, by now, historical developments. The best philosophical work since then is to be found in the history of philosophy—if one is lucky. One cannot help but wondering what turn philosophy would have taken if someone had picked up the revolutionary developments in logic and mathematics in the 1920s and directed them towards philosophy. Maybe there would still be logic courses in philosophy departments? Who knows? Recently a monograph has appeared which seems to ignore the respiratory epicycles of this modern philosophical slumber completely (and rightly so). Rudolf Carnap, a young German philosopher who is working at the University of Vienna, has the chutzpah to conceive a logischer Aufbau der Welt—a logical structure of the world—as if nothing had happened in philosophy in the last 80 years or so. Well, not much has happened indeed. If only a book like that had been published back then! Carnap’s main aim is to argue for the following thesis: give him any meaningful sentence from natural language or science; then this sentence can be reformulated in a precisely delineated conceptual framework of primitive expressions, exact definitions, and logical and mathematical rules. In fact, there are several possible choices for such frameworks, each one serving a different purpose, but what all of them have in common is that the hidden logical structure of the original sentence will become completely transparent through reformulation. That the target sentence is required to be nothing than a much more precise restatement of the original sentence means that both sentences ought to have the same truth conditions, by the laws of nature and by linguistic convention. Accordingly, each concept from natural language or science will have to be reconstructed in terms of a formally purified concept that has necessarily the same extension as its informal counterpart. This type of translation is possible, or so the thesis says, but it needs the application of logical and mathematical methods as the ones developed by Frege and Russell a long time ago. Of course, these authors have been forgotten by philosophers long since, but in light of Carnap’s book I urge people to reconsider their work: it is worth the effort, even though it means doing the unthinkable, that is, to learn some mathematics before one can philosophize. How does Carnap argue for his revolutionary claim? By concrete example. He erects a particular conceptual system and sketches how both common sense statements and scientific hypotheses may be reformulated within it. The conceptual system he chooses for the sake of demonstration is one that takes elementary first-person descriptions of immediate sense experience as its starting point: merely on the basis of logical concepts, mathematical concepts, and a binary concept of recollected resemblance between total experiences at a time, Carnap wants to express statements about sensory qualities, subjective temporal H. Leitgeb (&) Professor of Mathematical Logic and Philosophy of Mathematics, Department of Philosophy, University of Bristol, Bristol, UK e-mail: hannes.leitgeb@bristol.ac.uk