The Structure of Scientific Revolutions

The Structure of Scientific

Revolutions

Second Edition, Enlarged

Thomas S. Kuhn

VOLUMES I AND II • FOUNDATIONS OF THE UNITY OF SCIENCE

VOLUME II • NUMBER 2

The Structure of Scientific Revolutions

Thomas S. Kuhn

Contents:

PREFACE ...................................................... v

I. INTRODUCTION: A ROLE FOR HISTORY ............ 1

II. THE ROUTE TO NORMAL SCIENCE .................... 10

III. THE NATURE OF NORMAL SCIENCE ................. 23

IV. NORMAL SCIENCE AS PUZZLE-SOLVING ........... 35

V. THE PRIORITY OF PARADIGMS .......................... 43

VI. ANOMALY AND THE EMERGENCE OF SCIENTIFIC DISCOVERIES 52

VII. CRISIS AND THE EMERGENCE OF SCIENTIFIC THEORIES 66

VIII. THE RESPONSE TO CRISIS ................................. 77

IX. THE NATURE AND NECESSITY OF SCIENTIFIC REVOLUTIONS 92

X. REVOLUTIONS AS CHANGES OF WORLD VIEW ...... 111

XI. THE INVISIBILITY OF REVOLUTIONS ................. 136

XII. THE RESOLUTION OF REVOLUTIONS ................ 144

XIII. PROGRESS THROUGH REVOLUTIONS ................ 160

Postscript-1969 ................................................ 174

iii

Preface

The essay that follows is the first full published report on a project

originally conceived almost fifteen years ago. At that time I was a

graduate student in theoretical physics already within sight of the end

of my dissertation. A fortunate involvement with an experimental

college course treating physical science for the non-scientist provided

my first exposure to the history of science. To my complete surprise, that

exposure to out-of-date scientific theory and practice radically

undermined some of my basic conceptions about the nature of science

and the reasons for its special success.

Those conceptions were ones I had previously drawn partly from

scientific training itself and partly from a long-standing avocational

interest in the philosophy of science. Somehow, whatever their

pedagogic utility and their abstract plausibility, those notions did not at

all fit the enterprise that historical study displayed. Yet they were and

are fundamental to many discussions of science, and their failures of

verisimilitude therefore seemed thoroughly worth pursuing. The result

was a drastic shift in my career plans, a shift from physics to history of

science and then, gradually, from relatively straightforward historical

problems back to the more philosophical concerns that had initially led

me to history. Except for a few articles, this essay is the first of my

published works in which these early concerns are dominant. In some

part it is an attempt to explain to myself and to friends how I happened

to be drawn from science to its history in the first place.

My first opportunity to pursue in depth some of the ideas set forth

below was provided by three years as a Junior Fellow of the Society of

Fellows of Harvard University. Without that period of freedom the

transition to a new field of study would have been far more difficult and

might not have been achieved. Part of my time in those years was

devoted to history of science proper. In particular I continued to study

the writings of Alex-

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Preface

senschaftlichen Tatsache (Basel, 1935), an essay that anticipates many of

my own ideas. Together with a remark from another Junior Fellow,

Francis X. Sutton, Fleck’s work made me realize that those ideas might

require to be set in the sociology of the scientific community. Though

readers will find few references to either these works or conversations

below, I am indebted to them in more ways than I can now reconstruct

or evaluate.

During my last year as a Junior Fellow, an invitation to lecture for the

Lowell Institute in Boston provided a first chance to try out my still

developing notion of science. The result was a series of eight public

lectures, delivered during March, 1951, on “The Quest for Physical

Theory.” In the next year I began to teach history of science proper, and

for almost a decade the problems of instructing in a field I had never

systematically studied left little time for explicit articulation of the ideas

that had first brought me to it. Fortunately, however, those ideas proved

a source of implicit orientation and of some problem-structure for much

of my more advanced teaching. I therefore have my students to thank

for invaluable lessons both about the viability of my views and about the

techniques appropriate to their effective communication. The same

problems and orientation give unity to most of the dominantly

historical, and apparently diverse, studies I have published since the end

of my fellowship. Several of them deal with the integral part played by

one or another metaphysic in creative scientific research. Others

examine the way in which the experimental bases of a new theory are

accumulated and assimilated by men committed to an incompatible

older theory. In the process they describe the type of development that I

have below called the “emergence” of a new theory or discovery. There

are other such ties besides.

The final stage in the development of this essay began with an

invitation to spend the year 1958-59 at the Center for Advanced Studies

in the Behavioral Sciences. Once again I was able to give undivided

attention to the problems discussed below. Even more important,

spending the year in a community

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Preface

composed predominantly of social scientists confronted me with

unanticipated problems about the differences between such

communities and those of the natural scientists among whom I had

been trained. Particularly, I was struck by the number and extent of the

overt disagreements between social scientists about the nature of

legitimate scientific problems and methods. Both history and

acquaintance made me doubt that practitioners of the natural sciences

possess firmer or more permanent answers to such questions than their

colleagues in social science. Yet, somehow, the practice of astronomy,

physics, chemistry, or biology normally fails to evoke the controversies

over fundamentals that today often seem endemic among, say,

psychologists or sociologists. Attempting to discover the source of that

difference led me to recognize the role in scientific research of what I

have since called “paradigms.” These I take to be universally recognized

scientific achievements that for a time provide model problems and

solutions to a community of practitioners. Once that piece of my puzzle

fell into place, a draft of this essay emerged rapidly.

The subsequent history of that draft need not be recounted here, but

a few words must be said about the form that it has preserved through

revisions. Until a first version had been completed and largely revised, I

anticipated that the manuscript would appear exclusively as a volume in

the Encyclopedia of Unified Science. The editors of that pioneering work

had first solicited it, then held me firmly to a commitment, and finally

waited with extraordinary tact and patience for a result. I am much

indebted to them, particularly to Charles Morris, for wielding the

essential goad and for advising me about the manuscript that resulted.

Space limits of the Encyclopedia made it necessary, however, to present

my views in an extremely condensed and schematic form. Though

subsequent events have somewhat relaxed those restrictions and have

made possible simultaneous independent publication, this work remains

an essay rather than the full-scale book my subject will ultimately

demand.