The structural framework of the historian includes, among other things, divisions into historical periods. Obviously, periodization is the work of the historian, not of history. No objective or natural way of dividing up is to be found inbuilt into the historical course of events. This does not mean, however, that all ways of organizing the historical materials are equally good. In the historiography of modern science a tradition has arisen for working with chronological periods that follow the century in question: science in the 20th century, in the 19th, 18th and 17th centuries. The division is obviously arbitrary, in the sense that it does not reflect any internal tendency in the development of science. By chance, it would be reasonable to distinguish between the 19th and 20th centuries in the history of physics, whereas this is not the case in the history of biology or in the history of the earth sciences.

The periods used will normally be chronological so that the development is simply followed through linear time. But one does not have to regard chronologically simultaneous occurrences as being historically simultaneous too. For example, one could decide to place occurrences into periods according to their more or less natural connection in the hope that this would reflect the internal or logical development of science. If so, scientists who were ‘ahead of their time’ may be moved to the chronologically later periods to which they are thought to belong naturally.

The historical technique based on collective biographies and similar sources is called prosopography. What characterizes this method is that it uses data concerning many people and events as its sources.

Prosopography is not a method that is peculiar to history of science and it is only recently, in fact, that it has been introduced into this field in an elaborate form. This happened via inspiration from general social history, especially from economic history, that has long used quantitative methods of the same type as those used in prosopography. However, collective biographies have been used sporadically in the study of science for over 100 years, starting with Francis Galton (1822–1911) who compiled statistics about eminent British scientists so as to study the relationship between heredity, environment and genius. The statistical studies on geniuses made by Galton and others were strongly influenced by the extreme social-Darwinism of the Victorian age; today they are regarded as classic examples of so-called scientism. Wilhelm Ostwald used membership of scientific academies as a measure of ‘greatness’ and studied the distribution of members of such institutions with regard to sex, race, religion and nationality. Among other things, Ostwald concluded that women had no scientific ability and that Teutonic men had a particular aptitude for science (it is perhaps unnecessary to state that Ostwald was a German male). Studies of ability and genius like those of Ostwald and Galton are not, of course, comme il faut today, although their research methods in more refined forms have been taken over by modern quantitative sociology and historiography.

Histories of science involve particular perspectives, aims and methods of organizing materials that do not arise out of the objectively given past itself. Very often, history of science also serves a legitimating function. The fact that histories are written with commitment and from a particular motive, or may serve legitimating functions, does not necessarily imply that they are products of bad historiography (see also chapter 5). But as soon as documentary evidence is distorted, ignored or allocated disproportionate importance in order to fit in better with a particular moral that serves a social function, history becomes ideological.

I shall use the term ‘ideology’ in the sense that an ideological doctrine is a doctrine which legitimates the views and interests of a particular social group. This is a necessary but not a sufficient condition. The doctrine must also give a distorted or misrepresented picture of the reality it refers to. According to Althusser, an ideology is ‘a statement which, while it is a symptom of a reality that is separate from the reality it refers to, is a false statement in so far as it touches on the object it has in view’. The bias that is connected with ideological doctrines can be deliberate; but it will not normally be so. Ideologies are rarely admitted by the ideologists, nor by the social group to whose interests the ideology is directed.

Ideological historical writing covers a wide spectrum. At the one extreme there are outright ideological histories which serve, for example, political purposes. These ‘external’ ideologies are directed to the lay public or political bodies, serving a wider political function.

The legitimate criticism of the objectivity of historical facts is more concerned with when an occurrence is historical than with when it is a fact. It does not give grounds for doubts as to whether, after all, objectively true statements of fact about the past can actually be established. It is a fact that Caesar crossed the Rubicon in 49 BC and it is a fact that Darwin was born in 1802. Although data like this does not form the kernel of history, the simple establishment of facts is an important element in the process of historical research. The untangling of the facts is potentially valuable even if they cannot be explained at the time or placed in a historical context. The fact that the establishment of data is the result of a process of selection and is probably directed by subjective influences does not make the data less true or less objective. The most it can do is to make them less significant or less interesting. Many historians will regard it as of no consequence that Darwin was born in 1802, but what historian would seriously deny that Darwin was, after all, born in 1802?

When historians are interested in facts about the past it is because of their possible historical status, which, in practice, means their historical significance. We must therefore ask whether there are any objective (in the sense of absolute) criteria for the granting of the epithet ‘significant’ to some events and ‘insignificant’ to others.

The subject of the present work is what I consider to be the essentials of the historiography of science. I discuss a number of problems which, I suggest, are of fundamental importance to almost any serious historical study of science, irrespective of its particular field and period. There are, of course, historiographical issues which are peculiar to certain approaches, disciplines and periods. Most of these I have left untreated or only touched lightly. Thus science before 1500 only figures sporadically in the book, and issues peculiar to the social and institutional history of science have only received scant attention. Apart from these limitations there are other important topics which I do not discuss because they are only indirectly related to the main themes of the book. These include various philosophically based views concerning the historical development of science, such as the historiographical theories of Kuhn, Lakatos and others, and also the question of the so-called driving forces of scientific development.

The structure of the book is as follows. Chapter 1 gives an outline, separated from the rest of the work, of the prehistory of history of science. The chapters 2 to 7 deal with matters of a general historiographical nature, being an introduction to theory of history as applied to history of science. As a historical discipline, history of science is amenable to the same theoretical reflections which are valid in general history. Practitioners of the discipline, whether trained as scientists or historians, should be familiar with these reflections. In chapters 8 to 10 I discuss some of the basic problems in the general historiography of science.

According to the anachronical view, the science of the past ought to be studied in the light of the knowledge that we have today, and with a view to understanding this later development, especially how it leads up to the present. It is considered legitimate, if not necessary, that the historian should ‘intervene’ in the past with the knowledge that he possesses by virtue of his placement later in time. Anachronical historiography, in the sense being used here, involves a certain type of anachronism; but it is not necessarily anachronistic in the usual, derogatory sense.

Today, anachronical history of science is rarely a conscious historiographical strategy. On the contrary, there is broad agreement about praising a non-anachronical ideal. Even so, in practice, anachronical history of science is widespread and difficult to avoid. The doctrine is connected to the presentist view of history which may be seen as a theoretical justification of anachronical historiography. Furthermore, this perspective is legitimate from the points of view that regard the goal of history of science as primarily bound up with the present situation (cf. Chapter 3). If one believes that it is the task of the historian of science to understand the technical contents of older science and to pass this understanding on to the scientists of today, then a way of presentation that is anachronical in tendency will be natural. A text will then be taken to have been understood if its true contents, in the current sense, can be represented with modern formalism and using modern knowledge.

Several studies of the history of thermodynamics have followed this prescription.

Any evaluation of primary, published materials will involve the question of whether the text can really be attributed to the author; or how authentic an expression it is of the author's own thoughts. One cannot unquestionably assume that every word in a scientific publication is that of the author. There can be many reasons for this. It is well known, for instance, that for a long time there has been a tradition in academic institutions according to which professors, directors, head doctors and similar highly placed personnel appear as the authors of papers that have really been written by, and based on, the work of younger researchers. Furthermore, one must be aware of the fact that published sources have always to a certain extent been filtered through the apparatus of publication; that editors of periodicals, for example, might have changed the paper written by the author, sometimes quite a lot, and not necessarily with the consent of the author. In earlier times it was often the right or even duty of the editor to modify the material that was submitted, rather freely. In cases like this one cannot use the published source as a reliable expression of the exact views of the author. Today, scientific articles are criticized and edited by referees; the version that is published is often a second or third version of the original manuscript and thus not a suitable source of detailed information about the views of the author. Rough sketches and earlier unpublished versions of manuscripts will be much more suitable for this purpose.

Biographies of eminent, individual scientists are one of the oldest forms of history of science. However, in the new, professional history of science it has been regarded as a less-esteemed form of history, to some degree. It is only recently that this trend has been reversed. The diminishing respectability of the biography is connected with modern standards of scholarship in history of science and with a change in general perspective where the focus has to some extent moved to either intellectual or social topics. Biographical works are still, however, an important part of history of science and they will remain so. Even though biographies are often of dubious quality, as seen from a history of science point of view, they can carry out functions not covered by other forms of history.

Since the scientific biography is built up around the activities of an individual it can easily veer towards giving a distorted picture of the development of science. Namely by, in the very nature of things, concentrating on the achievements of the scientist whose life story is being told, and thereby possibly glorifying these, while other scientists merely appear as a grey background. The fact that a biography is written from a person-centred perspective does not in itself merit criticism and is not in itself a sign of lack of objectivity. The biographer, however, will often be tempted to identify himself with the subject and present the portrayed scientist as a hero; while his opponents and rivals are presented as villains. When this happens, the biography degenerates into so-called hagiography, uncritical black and white history.

Although the history of science as an autonomous academic discipline only developed in the 20th century, activities that might justifiably be described as early forms of history of science have been taking place for centuries. Historical descriptions and analyses have always followed the development of science. Indeed, even a superficial consideration of the history of science in former times reveals that many of the central historiographical problems discussed in modern history of science can also be encountered in earlier centuries.

Throughout most of the period in which science developed, it was learnt and cultivated as part of a historical tradition that was indistinguishable from science proper. In Classical times and in the Middle Ages in particular, the usual form of cultivation of science involved relating to earlier thinkers. Critical commentaries and analyses of the Classical works were made and these were used as a point of departure for new thought and contributions of current interest. When Aristotle wished to say something about atoms and the void, he reproduced parts of the history of atomism and embarked on a discussion with the long-departed Democritus. When a Greek mathematician wanted to solve a problem, the natural way to proceed was to begin by giving an account of the history of that particular subject, which was regarded as an integral part of the problem.

Classical historians were interested first and foremost in contemporary history and did not consider it of much value to consider earlier events or developments in a historical perspective.

The development of history of science during the last three decades has been characterized by a proliferation of methods and perspectives rather than by the emergence of a consensus as to what, exactly, constitutes the discipline. The eclecticism and the fact that the discipline includes separate, partly conflicting, interests makes it problematic to talk about the aim of the history of science. Nonetheless, many have taken on the task of stating what the superior aim of the discipline should be. In what follows we discuss some frequently articulated viewpoints. In chapter 10 we shall discuss the ideological role that history of science may play in connection with scientific disciplines and institutions.

I. It is sometimes asserted that history of science, when properly conducted, can have a beneficial influence on the science of today. In its most primitive form it is suggested that the practising scientist may profitably make direct use of the history of his science; that by studying the works of earlier scientists he may receive inspiration for a solution he is looking for or even find out that the solution had already been discovered by a predecessor in the discipline. Opinions of this kind were common in early history of science (cf. chapter 1), although it was difficult to find concrete examples of scientists who had directly benefited from their knowledge of history. Truesdell is one of the few modern historians who has dared to make the same assertion.

The term scientometry is used here to denote a collection of methods for analysing structure and development in science at a relatively highly developed level. As a methodological discipline, scientometry does not have any special object field; the methods can be applied in other social forms of organization than scientific ones, without any significant changes being necessary. Scientometry is not a particularly historical technique either although it is in that capacity that we will be concerned with it here. In fact, in many respects it is linked up with present science and must rather be called a quantitative sociology of science technique that can also be applied to parts of earlier science. In integrated studies of science – science of science – scientometry plays an important role as an instrument of analysis and prognosis for research policy.

One can distinguish between two kinds of studies within scientometrically orientated history of science, namely:

1. Studies that focus on the temporal development of science, quantified in various ways. Typically the development of scientific growth.

2. Studies that focus on the structure of scientific communication in a given period or on the influence of scientific contributions in the period. This form of history of science is close to many prosopographical and sociological studies.

Truly quantitative studies of history of science are a new phenomenon. The first completely quantitative history of science study – scientometrical in the sense we are using here – is from 1917, in which Cole and Eames applied bibliometrical methods to the history of anatomy.

A very considerable part of history of science is descriptive, that is, accounts of what occurrences took place and when they happened. In spite of this practice, almost all historians agree that history ought also to be explanatory. A pure description of the past will not qualify as real history but is what is somewhat condescendingly called chronicle writing.

Obviously, not all occurrences are in need of an explanation. In particular, it is the novel, non-trivial occurrences that we want to explain by grounding them in relatively familiar and known experiences. In the first instance, scientific occurrences ought to be evaluated and explained in accordance with the norm or norms prevailing at the time they took place. A period's norm can be regarded as everything that is taken for granted by the scientific community during that period. In this respect, the identification of the norms of a period is important. According to David Knight, ‘the recovery of the norm [is] itself interesting and must be the primary task of the historian’.

When a particular norm has been identified it can in itself constitute a basis for explanation. If we ask why a theory was accepted or why an experiment was interpreted in a particular way, a reference to the fact that it was in agreement with prevailing standards can in itself be an explanation. In contrast, a norm-breaking occurrence needs an explanation of its own. The norms that are used as a basis for explanation in such cases should, of course, be the norms of that time, not ours.

There are two main types of suggestion for what should count as an historical explanation.

Because of their placement in the past, historical occurrences cannot be re-created or manipulated. For this reason hypothetical or contrary-to-fact statements are often regarded as unacceptable in historical works. Thus Joseph Needham says: ‘Whether a given fact would have got itself discovered by some other person than the historical discoverer had he not lived it is certainly profitless and probably meaningless to enquire.’

A contrary-to-fact statement is a statement based on an assumption that is known to be factually false, in other words, that cannot be reconciled with the known facts. Such statements are also called counterfactual statements. They contain the conditional ‘if’ followed by the false statement P. ‘If X had not been the case, Y would not have taken place’ is a counterfactual statement in so far as X actually was the case (irrespective of whether Y occurred or not). X might, for example, be ‘Maxwell formulated the theory of electrodynamics’ and Y might be ‘the radio was invented’. In a certain sense the statement can be said to be a hypothetical statement about the past; but with the difference that the premise of the hypothesis (non-X) is known to be false. Hypotheses are normally statements whose truth value is not known, but which are used heuristically in order to deduce testable statements that will then support or weaken the hypothesis.

We cannot know whether the radio would have been discovered had Maxwell never lived; for we cannot remake the historical situation at the time of Maxwell without taking into consideration the fact that Maxwell did actually live.

A source is an objectively given, material item from the past, created by human beings; a letter, for example, or a clay pot. But this item is not in itself a source. It can be called a relic of the past or a source object. If the relic is to achieve the status of source-material it must be evidence from the past, it must tell us something about it. The relic must be capable of being utilized to give some of the information that it contains in a latent form. It is the historian who turns the relic into a source through his interpretation. By posing questions to it from particular hypotheses (that do not themselves need to have any documentary basis) the historian forces the source to disclose information. Unlike the relic, the source is not, as a source, a material item, but has to be regarded as information that has been released. The information disclosed by the source, and in that sense the source itself, becomes an interplay between the source object and the historian, a meeting between past and present. It follows from this that while the source object is fixed, the very same source can disclose different and possibly conflicting information.

In previous chapters we have seen that source materials are not given once and for all but that they originate in the dialectical process between the relics of the past and the interpretations of the present.

It is customary to distinguish between two different levels or meanings of the term ‘history’. History (H1) can describe the actual phenomena or events that occurred in the past; that is, objective history. In such expressions, for example, as ‘throughout history mankind's knowledge of nature has always increased’, history is to be understood as ‘the past’ or the phenomena that actually occurred in the past. But since we only have, and only ever will have, a limited knowledge of the reality of the past, most of what actually took place in the past will forever be beyond our grasp. The part of history (H1) that we do know is not just limited in extent but is also the product of a research process that includes the selections, interpretations and hypotheses of the historian. We do not have direct access to H1, only to parts of H1 that have been transmitted via various sources.

The term history (H2) is also used of the analysis of historical actuality (H1), that is, of historical research and its results. The object of history (H2) is thus history (H1) in the same way as the object of natural science is nature. Just as our (scientific) knowledge of nature is limited to the research results of science that are not nature but a theoretical interpretation of it, so our knowledge of the events of the past is limited to the results of history (H2) that are not the past but a theoretical interpretation of it.