UNIFIED SCIENCE

VIENNA CIRCLE COLLECTION

HENK L. MULDER, University of Amsterdam, Amsterdam, The Netherlands

ROBERT S. COHEN, Boston University, Boston, Mass., US.A.

BRIAN McGUINNESS, The Queen's College, Oxford, England

Editorial Advisory Board

ALFRED J. A YER, New College, Oxford, England

ALBERT E. BLUMBERG, Rutgers University, New Brunswick, N.J., US.A.

HERBERT FEIGL, University of Minnesota, Minneapolis, Minn., US.A.

RUDOLF HALLER, Charles Francis University, Graz, Austria

ERWIN N. HIEBERT, Harvard University, Cambridge, Mass., US.A.

JAAKKO HINTIKKA, Florida State University, Tallahassee, Fla., US.A.

GABRIEL NUCHELMANS, University of Leyden, Leyden, The Netherlands

ANTHONY M. QUINTON, The British Library, London, England

J.F. STAAL, University of California, Berkeley, Calif., US.A.

FRIEDRICH STADLER, Institute for Science and Art, Vienna, Austria

VOLUME 19

VOLUME EDITOR: BRIAN McGUINNESS

UNIFIED SCIENCE The Vienna Circle Monograph Series

originally edited by Otto Neurath,

now in an English edition

With an Introduction by

RAINER HEGSELMANN

Translations by

HANSKAAL

Edited by

BRIAN McGUINNESS

D. REIDEL PUBLISHING COMPANY ~.

A MEMBER OF THE KLUWER " ACADEMIC PUBLISHERS GROUP

DORDRECHT/BOSTON/LANCASTER/TOKYO

Library of Congress Cataloging-in-Publication Data

Einheitswissenschaft. English. Unified science.

(Vienna circle collection; v. 19) Translation of: Einheitswissenschaft, Bibliography: p. Includes index. l. Logical positivism. 2. Science - Philosophy. I. Neurath, Otto,

1882-1945. II. McGuinness, Brian. III. Einheitswissenschaft. IV. Title. V. Series. B824.6.E3713 1987 141'.42 87-26498

ISBN-13: 978-94-010-8218-1 e-ISBN-13: 978-94-009-3865-6 001: 10.1007/978-94-009-3865-6

Introduction and Articles 1-7 translated from the German by Hans Kaal

Published by D. Reidel Publishing Company, P.O. Box 17, 3300 AA Dordrecht, Holland.

Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers,

101 Philip Drive, Norwell, MA 02061, U.S.A.

In all other countries, sold and distributed by Kluwer Academic Publishers Group,

P.O. Box 322, 3300 AH Dordrecht, Holland.

All Rights Reserved © 1987 by D. Reidel Publishing Company, Dordrecht, Holland

Softcover reprint of the hardcover 18t edition 1987 No part of the material protected by this copyright notice may be reproduced or

utilized in any form or by any means, electronic or mechanical including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner

TABLE OF CONTENTS

EDITOR'S NOTE VB

INTRODUCTION by Rainer Hegselmann IX

THE MONOGRAPHS

1. OTTO NEURATH / Unified Science and Psychology (1932) 1

2. HANS HAHN / Logic, Mathematics, and Knowledge of Nature (1933) 24

3. RUDOLF CARNAP / The Task of the Logic of Science (1934) 46

4. OTTO NEURATH / What Is Meant by a Rational Economic Theory? (1935) 67

5. PHILIPP FRANK / The Fall of Mechanistic Physics (1936) 110

6. Towards an Encyclopedia of Unified Science (1937). Lectures by Otto Neurath, Egon Brunswik, Clark L. Hull, Gerrit Mannoury, and J.H. Woodger 130

7. RICHARD VON MISES / Ernst Mach and the Scientific Conception of the World (1938) 166

8-9. HEINRICH GOMPERZ / Interpretation: Logical Analysis of a Method of Historical Research (1939) 191

NOTES 273

INDEX 298

V

EDITOR'S NOTE

This volume contains in English the entire series of monographs with the title Einheitswissenschaft that Otto Neurath, with the collaboration of varying groups of colleagues, edited between 1933 and 1939. The authors, members of the Vienna Circle and a number of associated thinkers, set out to demonstrate in a programmatic way how the thesis of the unity of science could be established for a wide variety of areas of study. More systematic treatment was reserved for the Encyclopedia of unified science, while problems of detail or of controversy were first treated in Erkenntnis (The journal of unified science). The history and rationale of this procedure is discussed in Rainer Hegselmann's intro­duction.

That introduction, and the first seven monographs, have been trans­lated by Hans Kaal. Satz, always a difficult word, has generally been rendered by "proposition", but in the cases of Carnap's contribution and the earlier of Neurath's two, "sentence" seemed to be demanded. The double monograph that comes last is in Gomperz's own scholarly English. A very few residual Germanisms have been silently corrected.

Graz, June 1986 B.McG.

VB

RAINER HEGSELMANN

UNIFIED SCIENCE:

THE POSITIVE POLE OF LOGICAL EMPIRICISM

1. THE PLACE OF UNIFIED SCIENCE IN THE PROGRAMME OF

LOGICAL EMPIRICISM

The idea of unified science is not a peripheral consequence of the philosophy of logical empiricism; it is, rather, of central importance to it. To be able to determine more precisely the role and function of the idea of unified science, we need to get to the core of logical empiricism, the source of its theoretical identity, and to get there, we need to consider first of all the interest underlying logical empiricism and se­condly the fundamental assumptions motivated by that interest. 1

First, the origin of logical empiricism falls in a period of sweeping advances, not only in the natural sciences and in particular in physics, but also in mathematics and logic. Of central importance for an under­standing of the genesis of logical empiricism would seem to be the fact that this sweeping scientific advance was directed precisely against that philosophical conception which could reasonably be regarded as the modern foundation of the sciences, namely Kantian transcendental philosophy. To be able to explain the supposedly apodictic character of fundamental physical laws (Newtonian mechanics and the law of the conservation of matter), Kant had declared these laws to be synthetic judgements a priori. Kant had given the same status also to the judge­ments of mathematics, and for a similar motive: to reconcile the appa­rent apodictic character of these judgements with their alleged informative content which in his opinion had frequently been overlooked. An existen­tial presupposition as regards synthetic judgements a priori had appa­rently crept into his project of a "critique of pure reason" and into the initial question that had guided his investigations, "How are synthetic judgements a priori possible?" It is precisely this presupposition which could reasonably be taken to be false, following some decisive break­throughs in physics, mathematics, and logic. In physics, a scientific revolu­tion at the beginning of the century led to the replacement of Newtonian mechanics by Einstein's theory of relativity. From a Kantian perspec­tive, this amounted to a rejection of a system of synthetic judgements

IX

x INTRODUCTION

a priori, and what is more, to a rejection based ultimately on a posteriori findings; in other words, the "pure" science of nature in Kant's sense of the term had proved to be, not only not pure, but even false. As for logic and mathematics, the decisive works of Frege, Russell, and White­head suggested two conclusions: first, that it was possible to construct mathematics on the basis of logic (logicism), and secondly, that logical propositions had an irrevocably analytic status. But within the frame­work of logicism, the status of logical propositions is passed on to mathematical ones, and mathematical propositions are therefore also conceived of as analytic. All this creates a situation where the existential presupposition contained in the Kantian question about the possibility of judgements that are both synthetic and a priori must, it seems, be rejected as false. But to drop this presupposition is, at the same time, to strike at the very core of Kant's programme of putting the natural sciences on a philosophical foundation. The failure of the modern attempt to do so suggests at the same time a reversal of the relationship between philosophy and the individual sciences: it is not the task of philosophy to meddle with the foundations of the individual sciences; being the less successful discipline, its task is rather to seek guidance from the principles of rationality operative in the individual sciences. A philosophy of the future would therefore have to meet the most strin­gent requirements with respect to verifiability and intersubjectivity. The interest in a rational philosophy in this sense must be regarded as the constitutive interest of logical empiricism.

Secondly, the interest in such a rational philosophy is not by itself sufficient to differentiate logical empiricism from other movements. The same interest can be ascribed to Husserl's phenomenology or even to Neokantianism as a constitutive element. There are, however, two fundamental assumptions which are specific to logical empiricism and which are connected, in this context, with this constitutive interest. In this context, these fundamental assumptions can be understood as theoretical reactions to the failure of the Kantian programme: they point to those principles which Kant did not observe and to the non­observation of which one can trace back the difficulties his transcenden­tal philosophy ran into.

The fact that the paradigm cases of synthetic judgements a priori could no longer be maintained in the light of scientific advances might at first be interpreted to mean that there was something fundamentally absurd in the assumption that there were such judgements: being

INTRODUCTION xi

synthetic and being a priori seem to be incompatible, and being a posteriori seems to be a necessary presupposition for a judgement's being synthetic. Such a diagnosis is obviously suggested by the fact that among the cases of synthetic judgements a priori adduced by Kant the physical ones had proved not to be a priori and the mathematical ones had proved not to be synthetic. This diagnosis could then be expressed in the form of the following epistemological principle: knowledge can be gained only by experience. This first fundamental assumption of logical empiricism will be called the base theorem.

The assumption that there were no synthetic judgements a priori, added to the fact that all decisive scientific advances were achieved either in the field of synthetic judgements a posteriori or in the field of analytic ones, provided the motive for the further assumption that judgements with sense could be made only within the field of these two kinds of judgement: empirical and analytic judgements seem to be the only kinds of judgement that admit a question as to the truth-value of a judgement. On the other hand, those "propositions" that cannot have a truth-value assigned to them, not even in principle, seem to be senseless linguistic formations. For what could a proposition state or mean, what ~ould be its content, if it could not even in principle be said to be true or false? To generalize, it is possible to distinguish between propositions with sense, which are either true or false, and senseless pseudo­propositions, which merely imitate the grammatical form of proposi­tions with sense. In this context, "true" and "false" are predicates which can evidently be applied only to empirical and analytic propositions. The second fundamental assumption, as just formulated, will be called the sense theorem.

Against the background of the base and sense theorems, it is no wonder that logical empiricism, especially in its early phase, saw itself as being in the forefront of a battle against traditional philosophy, for as is obvious even from its own claims, the latter takes itself to be an enterprise that is in large part neither empirical nor analytic. But if this is so, then the propositions of a philosophy so understood must fall eo ipso into the field of senseless pseUdo-propositions. While the proposi­tions of a fairy tale may still be false, the propositions of philosophical metaphysics are not even that. What is expressed in metaphysics cannot therefore be called an erroneous claim to knowledge; it must be some­thing entirely different. Moritz Schlick tried to elucidate the way meta­physics functions by introducing a distinction between immediate

Xll INTRODUCTION

experience and incommunicable, because entirely private, experience: on the basis of this distinction, metaphysics may be called a fruitless attempt to communicate what cannot be said because it can only be experienced.2 Carnap's diagnosis was very similar: metaphysics is not knowledge, but an expression of the feeling for life, albeit in the wrong medium. He put it in a most graphic manner: "Metaphysicians are musicians without musical ability. In its stead, they have a strong inclination to work in the medium of theory, to string together concepts and thoughts. But instead of exercising this inclination in the field of science on the one hand and, on the other, of satisfying the need for expression in art, the metaphysician mixes up the two things and creates a structure which is completely useless for knowledge and inadequate to the feeling for life.,,3 Given such a verdict on metaphysics, it is obvious that it cannot be one's task to refute metaphysics, for the negations of senseless propositions are themselves senseless. All that is required is some relatively rough and ready clearing-up operations. Thus in the programmatic paper, "The Scientific Conception of the World: The Vienna Circle", published jointly by Carnap, Hahn, and Neurath, the authors say, in speaking of the representatives of logical empiricism: "They set to work with confidence to clear away the logical rubble of millennia. ,,4

This yields the first central consequence of the fundamental assump­tions of logical empricism: it follows from the sense and base theorems that logical empiricism must take a critical and negative attitude towards traditional metaphysics. But this brings us at the same time to the programme of unified science, which is the positive task that logical empiricism sets itself and which can be understood as the second central consequence of its fundamental assumptions.

It can be said as a matter of principle that under the name "unified science" is to be understood the totality of those propositions that are legitimate according to the sense and base theorems. The emphasis on unification is here directed against a frequently assumed hiatus between the social or "mental" sciences on the one hand and the natural sciences on the other. As against this, logical empiricism emphasizes that it follows from the sense and base theorems that all synthetic sciences are to be formulated in one language whose descriptive constants either themselves refer to what can be immediately experienced, in which case they belong to an unproblematic elementary field of simple fundamental predicates, or at least can be reduced to that fundamental vocabulary via

INTRODUCTION XIll

explicit definitions - or at the very least connected with it by reducing at least part of their meanings, the latter being the more liberal alternative. Neurath in particular favoured as the fundamental vocabulary a so­called "physicalistic" language, whose fundamental descriptive vocabu­lary expressed properties and relations that could be localized in space and time, contrary to Carnap for example who, in The Logical Structure of the World, had used a phenomenalistic language in his constructions.5

In his later works, Carnap followed Neurath's conception. It thus appears that the thesis of physicalism, understood as the obligation to use a physicalistic vocabulary, represents a sharpening and tightening of the programme of unified science. Neurath is therefore able to speak in this sense of the "unified science of physicalism" as one of the charac­teristics of the Vienna Circle. 6

Thus the programme of physicalistic unified science does not affirm that the laws of any science can be reduced to the laws of physics, but merely that the propositions of any ~cience should be expressed in one particular language. Carnap first envisaged the way towards unified science along these lines: the language of physics would first be reduced to the elementary physicalistic language (object language), and the language of biology would then be reduced to that of physics, and the language of psychology to that of biology.

The question of the relationship between philosophy and unified science did not receive a uniform answer within the Vienna Circle. If empirical and analytic propositions alone have sense, then the first question that arises is how it is even possible to have a philosophy which is not open to condemnation as metaphysics. Following Wittgenstein's conception, Moritz Schlick took the view that the task of philosophy did not, as had been thought, consist in establishing peculiarly philosophical propositions, but rather, that philosophy reduces to the logical clarifica­tion of thoughts. Philosophy, so understood, escapes condemnation as metaphysics by being an activity, and by neither consisting of nor leading to specifically philosophical propositions. 7 However, this con­ception of philosophy itself rests on a problematic conception, that of the philosophy of language of the Tractatus Logico-Philosophicus, according to which it is not possible for a proposition both to have a sense and to be about language. Neurath in particular did not follow that philosophical conception of language. But in that case it becomes possible to have a philosophy at least in the sense of a syntactic analysis of the language of the sciences, a conception which puts "logical

XIV INTRODUCTION

syntax", as Carnap calls one of his central writings,8 in place of philo­sophy. Later on, after recognizing also the importance of semantic and pragmatic questions, Carnap declared that the "logic of science", as he called it, which had the task of giving a comprehensive metatheoretical analysis of the sciences, would be the discipline to succeed philosophy. A logic of science, so understood, which systematizes what can be said with sense about propositions, becomes in turn an integral part of unified science, which then amounts to the totality not only of what has sense but also of what is - or at any rate is intended to be - true, tenable, or plausible.

It was clear, especially to Neurath and Carnap, that in envisaging the programme of unified science they were envisaging a major project which required the greatest theoretical effort and could be realized only on the basis of countless analyses and only in collaboration with a large number of fellow-workers. But at the same time, in proposing the programme of unified science, they were setting their sights on that positive pole which according to the fundamental assumptions of logical empiricism was necessarily the only course open to them after the shipwreck of all traditional philosophy. This would explain why Neurath writes with such emphasis: "Metaphysical terms divide - scientific terms unite. Scientists, united by a unified language, form a kind of workers' republic of letters, no matter how much else may divide them as men. Philosophers on the other hand are comparable to the feudal lords of San Gimignano. They sit in their lonely towers in the dark of night and seek to guard themselves against their neighbours by raising their towers ever higher and higher. But beinE in the dark, they are afraid and sing aloud - and Freud is right in what he says of thore wandering philoso­phers who also sing aloud in the dark forest: while this may lessen their fear, it does not enlighten the world. ,,9

2. THE HISTORY OF THE SERIES EINHEITSWISSENSCHAFT

The thesis of unified science as the positive pole of logical empiricism can also be demonstrated in other, nonsystematic ways. It is well supported, e.g., by the fact that the term "unified science" appears as the title of a series of writings most closely connected with logical empiricism, namely the series which is being reissued here. Moreover, the term found its way, in a programmatic manner, into the title of the largest publication project to which the logical empiricist movement was

INTRODUCTION xv

to give birth, namely the International Encyclopedia of Unified Science. It is also significant that the journal Erkenntnis was renamed The Journal of Unified Science.

The founding of the series Einheitswissenschaft is due directly to Neurath's initiative. Its creation provided him with an organ, not only for publicizing the first basic orientations of the programme of unified science, but also for publishing the first attempts at integrating the sciences into a single whole. Neurath must have intended it at the same time as a demonstration of what the series was intended to do when, in the first number entitled "Unified Science and Psychology", he took up the question how psychology can be incorporated into unified science and tried to show how the clashes of opinion between such initially divergent schools of psychology as behaviourism, gestalt psychology, reflexology, individual psychology, and psychoanalysis could become fruitful exchanges of ideas after a physicalistic reconstruction of their language. 10

The series Einheitswissenschaft, up to and including number 5, was published by Gerold & Co in Vienna under the direction of Heinrich Neider, who should also be counted as a member of the Vienna Circle. Number 1 was edited by Neurath in collaboration with Carnap, Frank, and Hahn, and number 2 in collaboration with Carnap and Hahn. After Hahn's unexpected and untimely death in 1934, Neider suggested bringing in a new coeditor, which led to the acquisition of 10rgen 10rgensen, about whom Neurath wrote with genuine affection in one of his letters to Carnap: "I believe that of all of us he alone does his worst as a critic of our era.,,11

The collaboration between Einheitswissenschaft and Erkenntnis did not proceed quite as smoothly as Neurath would have wished. Neurath had to ask Carnap more than once to see to it that the first three numbers of the collection Einheitswissenschaft would be reviewed in Erkenntnis, and he had expressed the wish that number 1 (0. Neurath, "Unified Science and Psychology") be reviewed by Hempel, number 2 (H. Hahn, "Logic, Mathematics, and Knowledge of Nature") by Frank, and number 3 (R. Carnap, "The Task of the Logic of Science") by 10rgensen. Carnap in turn placed the responsibility for the delays and mix-ups in the review section of Erkenntnis on Reichenbach. He had supposedly been trying and trying in vain to get Reichenbach to give him a list of the books still to be reviewed with the names of the prospective reviewers. Carnap then proposed Kurt Grelling as a

XVI INTRODUCTION

reviewer for the first three numbers, which for Neurath was an unhappy choice, for as Neurath put it, the collection called for a reviewer who agreed with the movement, which was not to be expected from GrellingY Neurath was to see his opinion confirmed when Grelling in his review took Neurath to task for frequently disposing of quite serious problems by simply waving them away. 13

After the invasion of Austria by German troops in March 1938 it was clear to Neurath that Einheitswissenschaft could no longer be published in Vienna, and he therefore asked Carnap to negotiate with the Univer­sity of Chicago Press about taking over the series. At that time, numbers 2 and 3 were already out of print, and numbers 6 and 7 were in the hands of Gerold & Co ready to be printed. But when in April 1938 Neurath was offered the possibility of finding a home for the collection Einheits­wissenschaft with Van Stockum & Son in the Netherlands and of continuing it as the Library of Unified Science, he promptly seized the opportunity. After the Springer Publishing House in March 1938 ceased publication of the Schriften zur wissenschaftlichen Weltauffassung edited by Schlick and Frank, another publisher had to be found for that series too, and following a proposal of Carnap's, the Library of Unified Science was subdivided into a "monograph series" and a "book series". Neurath acted as editor-in-chief and Carnap, Frank, J0rgensen, and Morris as associate editors. While numbers 6 and 7 were still published in 1938 by Van Stockum & Son under the title Einheitswissenschaft -Unified Science - Science unitaire (the publisher also took over the remainder of the collection), number 8-9, composed by Heinrich Gom­perz, was published in 1939 as the first monograph in the new Library of Unified Science.

In the years 1938 to 1940, Van Stockum & Son became in effect the publishers of the logical empiricist movement, after Erkenntnis too could no longer be published by the Felix Meiner Publishing House, and after it too was taken over by Van Stockum & Son. Until 1937 Erkennt­nis could still be published in Germany, even though the editorial work was already being done from abroad. In July 1937, the National Socialist administration, or more precisely, the so-called Reichsschrifttumskam­mer, began to put pressure on the Felix Meiner Publishing House. In a letter to Rudolf Carnap, Felix Meiner reports that he has been informed that "the continued presence of Professor Reichenbach on the editorial board of Erkenntnis is intolerable, not only because he is non-Aryan, but mainly because in the post-war period he has expressed political

INTRODUCTION XVll

views in his speeches and pamphlets which have made him unacceptable to the present government."14

Meiner then adds that, at least according to one informant, the Reichsschrifttumskammer is nevertheless well aware that in the case of international journals "a certain percentage of Jewish collaborators" cannot be avoided. 15

Carnap and Neurath wanted Erkenntnis to be published as long as possible in Germany, and faced with this kind of "antisemitism with a pragmatic twist", they thought of a solution which would have had the overall effect of making Reichenbach a member of a wider editorial committee. However, this was not to be, for Meiner suspended work on Erkenntnis in September 1937, and for reasons which highlight at the same time the situation of scholarly and in particular philosophical circles in Germany in 1937. Meiner writes: "While the ministry agreed to the proposed solution, at least according to a verbal communication by my informant, this does not, however, prevent others in scholarly circles from agitating below the surface against my publishing house by letting it be known that I shall not be in a position to see to it that no Jew will ever publish in this journal. And there are circles who find it impossible to publish anything in a house that still has anything what­soever to do with Jews ... I find this very distressing. For if I had been able to anticipate that the official scholarly circles would exceed the ministry in their demands, I could have saved you and myself these difficult negotiations.,,16 Thereupon Erkenntnis was bought up by Van Stockum & Son, while the University of Chicago Press took over distribution on the American continent. At the same time, the journal was given the title The Journal of Unified Science (Erkenntnis).

In view of considerable delays in the delivery of the journal to the United States, Carnap and Morris proposed in April 1940, just before the German attack on Denmark and Norway, that both the Library of Unified Science and The Journal of Unified Science be produced by the University of Chicago Press, while Van Stockum & Son would merely be the agent for Europe - which would have reversed the previous arrangements. When news of the German attack on Denmark and Norway reached Carnap on 9 April 1940, Carnap concluded that there was no way to avoid moving both publications to the United States. 17 At the end of April 1940 he was no longer even ready to send the finished manuscript of Introduction to Semantics to Europe (where it was sup­posed to appear in the Library of Unified Science) because the risks of

XVlll INTRODUCTION

loss and delay were too great. 18 Neurath reacted in a very different way to the events that overtook one another so dramatically after April 1940. As late as 6 May 1940, that is, four days before the German surprise attack on the Netherlands and Belgium, he wrote to Carnap: "Relying on my information, Van Stockum & Son have decided to take on the Library and the Journal . ... The publishers have now invested much money, started with the publicity, and exposed themselves to considerable risks because they hope and expect that what they have taken on courageously at a difficult time will payoff later on. As you will understand, I feel morally responsible towards the publishers. Your letter has affected me deeply. There is no way I can tell the publishers such a· thing .... But it is not just because of this moral obligation that I think it very important not to embark on any changes as long as it is not absolutely necessary. Small foreign countries are expected to stand up and not simply to collapse. But this means that one must avoid anything that would produce defeatism. If the publishers themselves were afraid or wanted to limit their production etc., then it would be fighting against windmills to want to support them. But there is no question of this .... You speak of Europe as a continent in decline. Maybe something decisive will actually happen, maybe - but all one can do is think carefully about what to do if it comes to the worst. But I am not in favour of taking preventive measures which, if we do not tell Van Stockum about them, will seem unfair and, if we do tell them, will ruin the chance of continued faithful collaboration and will actually have a defeatist effect. "19

The same spirit underlay Neurath's vain attempts to find an English publisher for the Library and the Journal after his flight to England. "We have to rebuild Europe, do not forget it", he admonished Carnap [in English] in a letter dated 21.9.1941. As for the Library of Unified Science, the failure of the attempt to find an English publisher for it meant that the first number that had appeared under the title Library of Unified Science had at the same time been the very last one of the series.

3. OTTO NEURATH AS THE INDEFATIGABLE ORGANIZER OF UNIFIED SCIENCE

It will not detract from anyone else's merits if we say that Otto Neurath was the effective driving force behind all efforts towards unified science. Besides the editorship of the series Einheitswissenschaft, he took on the

INTRODUCTION XIX

decisive organizational work for the five international congresses on the unity of science which were held between 1935 and 1939 in Paris, Copenhagen, Paris again, Cambridge (England), and Cambrige (USA). It was he also who, starting in 1934 and from The Hague, carried out a large part of the editorial work on Erkenntnis or, as it came to be known, The Journal of Unified Science. The idea of summing up the essential parts of unified science in an encyclopedia must have come to him very early in his career. Morris reports that Neurath had enter­tained the project of an encyclopedia already in the twenties and had had exploratory talks about it with Hahn, Einstein, Frank, and Carnap. The Mundaneum Institute he had founded in The Hague had been working on the project since 1933. At the First International Congress on the Unity of Science Neurath presented to the public the project of an encyclopedia of unified science, and on a motion by Morris the congress approved the plan. At the same time an encyclopedia commit­tee was formed consisting of Carnap, Frank, J0rgensen, Morris, Neu­rath, and Rougier. The encyclopedia was to be published under the title International Encyclopedia of Unified Science. The encyclopedia project as a whole was enormous in scope. According to Neurath's plan, the encyclopedia was to consist of four sections. Section 1 was to lay the foundations of unified science; section 2 was to treat of methodological questions; section 3 was to give a synoptic view of the current state of the individual sciences. Section 4 was then supposed to present the application of the results and methods of the sciences to medicine, law, engineering, etc. Each of these sections was to consist of several vol­umes and each volume of ten monographs. In total, Neurath was thinking of 26 volumes and 260 monographs. Beyond this he was planning a supplement of ten volumes which was to contain nothing but maps and graphs. The work was to appear in English, French, and German.

Neurath was obviously the organizational driving force behind the logical empiricist movement. But Neurath was certainly also a theorist of logical empiricism, and to this extent he was certainly not just an "honest broker", as he repeatedly called himself in his letters to Carnap.20 Among his theoretical contributions the following deserve special men­tion: his insistence on a physicalistic language, the coherence theory of truth, his criticism of the exaggerated hopes attached to formalization and definition, his contributions to the question of protocol sentences, his emphasis on decision in the acquisition of knowledge, his contributions

xx INTRODUCTION

to the idea of unified science and in particular his attempt to integrate sociology and psychology into unified science, and finally - though one could easily go on - his criticism of Popper which was far ahead of its time and in which he aiready anticipated the essential arguments of the debate involving Kuhn, Lakatos, and Feyerabend. 21

All the same, Neurath's position within the Vienna Circle or more generally within the logical empiricist movement was not a simple and unproblematic one. Schlick is known to have made somewhat derogat­ory remarks about Neurath on more than one occasion. Conversely, Neurath was extremely critical of Schlick, as is shown especially by the correspondence between Neurath and Carnap. For example, when Neurath learned from Carnap that Schlick was prepared to found a society to succeed the Ernst Mach Society, which had been dissolved in 1934 by the Dolfuss regime, even though he was not allowed to use the term "unified science" in the name of his society, Neurath reduced Schlick's whole attitude to the formula "pro-Dolfuss, anti-unified­science" .22 Hahn frequently hurt Neurath's feelings by teasing him, as when Hahn spoke of Einheiz- instead of Einheits-wissenschaft [from einheizen, literally to heat, but with a range of transferred senses including to egg on or to hector].23 Already in the thirties, Neurath had frequently asked Carnap to make it clearer in his publications what was due to him, Neurath, by giving appropriate references and citations. In the end, there arose a conflict between Neurath and Carnap which struck at the heart of their long-time friendship, a conflict sparked off by the appearance of one of Neurath's writings, Foundations of the Social Sciences. This work was to appear as fascicle 1 of volume 2 of the encyclopedia, which was being edited jointly by Carnap, Morris, and Neurath. Because of his sudden flight following Nazi Germany's sudden attack, Neurath had to leave the first draft of the work behind in Holland. He then wrote a new draft in England, but due to various fortuitous circumstances Carnap got to see it only at a time when it was for various reasons no longer possible to make changes in it. But since Carnap regarded the work as in need of revision, so much so that he did not want to be responsible for it as coeditor, he had a footnote added saying that for various reasons he assumed no responsibility for this fascicle. Neurath felt deeply wounded by Carnap's conduct. He could no longer regard this incident as an isolated case, but took it rather for a typical example of the way he had been treated within the Vienna Circle and within the logical empiricist movement in general. In the course of

INTRODUCTION XXI

this quarrel, which was carried on in several letters back and forth, Neurath also confessed that if he had finally been forced to found the series Einheitswissenschaft, it was because the articles he had written for Erkenntnis had been rejected. 24

We still lack an exact analysis of Neurath's role and significance within the Vienna Circle and for logical empiricism as a whole, an analysis which would certainly be desirable. To anticipate hypothetically such an analysis, we may, however, conjecture that the difficulties Neurath encountered and the conflicts in which he got involved can be traced back, at least as far as the kernel of rationality they contain is concerned, to the programmatic character of his writings, which was often very strong. For example, Neurath's discussions of semantic questions stand in stark contrast, from the point of view of precision and detail, to Carnap's elaborations of them in his Introduction to Semantics,2s a work which gave rise to a bitter quarrel between Carnap and Neurath because Neurath considered it to be metaphysics pure and simple. 26 But while Neurath's reflections on semantics are indeed short on detail, they are at the same time full of promise, for they can be understood as a programmatic nominalism. In other words, programmatic works can very well point the way to the future, as can also be demonstrated for example in the case of Neurath's critique of Popper.

As a provisional verdict on Neurath one might cite what Carnap said [in English] about Neurath's significance for logical empiricism in the last letter he was able to write to Neurath (Neurath died on 22.12.1945), a letter which is at the same time characterized by an effort to settle the quarrel that had broken out between them: "Your temper and way of acting is different from most of us; it is more energetic, active, aggres­sive. Consequently, it has fallen to you to be the driving force in our movement and all its various activities. We all are grateful and apprecia­tive for this; we all realize where our train would still be stuck if we hadn't had the big locomotive."27