My subject is the history of science in antiquity, where the convention I adopt for “antiquity” is that it covers everything from the earliest recorded Mesopotamian investigations in the third millennium BCE down to the end of the third century CE, by which time two particularly significant upheavals had taken place at either end of the Euro-Asia land mass. I refer to the Christianization of the Greco-Roman World and the rise of Buddhism in China. That study poses a number of distinctive problems, both substantive and methodological, which I shall go on immediately to identify. At the same time it is particularly worthwhile, in my view, for the light it can throw on very early efforts at understanding the physical world. Let me give a brief preliminary explanation of my main thesis.

Many of us now assume that science gives robust answers to what there is to investigate, how it should be investigated, and what science itself is good for. But we may ask, first, what were the views of those who first embarked on attempts to increase understanding of the physical world, what counted as understanding for them, and under what pressures, intellectual, social, or political did they work? Of course they were not to know what was to come, but that means that our examination of their views is all the more interesting and open-ended. Then secondly are we content to believe that we do indeed now have stable if not definitive answers to those three questions ourselves? If we too face, as we surely do, uncertainties concerning what science can and should deliver, it is worthwhile to reflect on how our very early predecessors got on. I shall endeavor to elucidate these points in what follows.

But the first major difficulty we encounter is whether we can describe any of the work of ancient investigators as “science” in the first place? No ancient society had a term that is equivalent to our “science.” They spoke in terms of disciplines that had labels that correspond, rather, to “learning” or “knowledge” (Greek episteme, Latin scientia, Chinese xue) or “inquiry” (Greek historia, e.g. “concerning nature,” peri phuseos, Chinese ge wu, the exhaustive investigation of things). So one major recurrent issue we face is this: how far is it the case that any talk of science in the ancient world is straightforwardly anachronistic and is bound to distort the ancients' own performance?

Then to that substantial difficulty we have to add one that concerns the evidence available to us. Whereas historians of early modern and contemporary science dispose of ample documentation, concerning the biographies of scientists, the collectivities to which they belonged and the social, economic, and political background against which they did their work, the historian of the ancient world has to make do with evidence that is both lacunose and biased, though it is, of course, impossible to quantify just how much has been lost or to be confident we have identified all the important biases. We have, for sure, many complete texts that have been preserved, often because they achieved canonical status at some point. In mathematics Euclid's Elements did so in the Greco-Roman world, as did the Jiu Zhang Suan Shu (Nine chapters on mathematical procedures) in China, and analogously in medicine there are the Hippocratic and Galenic corpora and the Chinese medical classic the Huang Di Nei Jing.

But for many ancient investigators, the pre-Aristotelian atomists, and many Chinese thinkers of the Warring States period such as the Mohists, for example, we simply do not have adequate original texts. We are left to try to reconstruct their work mainly from sources that are unsympathetic, when not downright hostile. When that happens ancient prejudicial interpretations skew the picture even before we come to further modern distortions.

Some might conclude that the obstacles our inquiry faces make it not just all but impossible, but pointless, though that is surely premature. Any results that we might reach must, to be sure, be acknowledged to be highly tentative and provisional, and the answers to many questions simply elude us. In fact it has often proved necessary, when new evidence has become available from papyri from Egypt, or from texts and artefacts from Chinese tombs, to make major revisions to previously accepted beliefs. Yet from one point of view the very difficulty of our investigation, and the way in which it implicates philosophy of science, make it more, rather than less, interesting and worthwhile. We are forced to open up fundamental issues to do with the nature of science and the origin of scientific ambitions.

Should we take a broad view, according to which science is a matter of the systematic observation, description, classification, explanation, prediction, and control of natural phenomena? In which case, are we dealing with universal human aims, and if indeed we think that, how do we account for their very different manifestations in ancient and modern societies? What are the necessary and sufficient intellectual or social conditions that allow such diverse inquiries to be initiated? That is an easy enough question to formulate, but one that proves formidably difficult to answer.

Or should we adopt a narrower, admittedly more conventional, view, that science depends on well-defined methods and purpose-built research institutions? If so, that still leaves us with the important task of tracing how any such methods came to be established and the institutions created. That may be the special job of the historian of early modern science, but it is one to which the study of even ancient endeavors can also contribute. After all, sustained efforts were made already in ancient Mesopotamia, China, and Greece especially, to understand the movements of the heavenly bodies, including the cycles of eclipses, to determine the shape and the size of the earth, to plot the courses and the causes of diseases, to classify animals and explore the ways they reproduce, and many other matters, though not all those investigations were pursued in all three ancient civilizations and the importance and relevance attached to those that were varied appreciably.

It is clear that both the how and the why of the writing of the history of ancient science are distinctive. First as to the how, any study of the remote past requires deep immersion in every aspect of the societies concerned, the mastery of ancient languages, and familiarity with every type of textual and other evidence. Nor, I have now personally come to believe, is it enough to study just one ancient civilization. We have to guard against any assumption that what applies to the way in which inquiries were conducted and developed in one society holds true equally of others. So often in the past historians of Greco-Roman antiquity have imagined that their findings give access not just to one way in which astronomy, or mathematics, or medicine, or zoology and botany developed, but to the way in which each of them had to.

But as has become increasingly clear as the study of Mesopotamian and Chinese inquiries has progressed during the last few decades at the hands of Otto Neugebauer, Joseph Needham, and their successors, there are considerable divergences in the way those disciplines grew, in the aims that investigators set themselves and how they pursued them. There was no one royal road by which science had to develop. That applies even to a subject such as mathematics, where we might think that both the methods and the aims of the discipline would be cross-culturally invariant. The comparative history of the field shows that that is simply not the case. To mention just one of the most obvious examples, some mathematical traditions did, but most did not, set great store by axiomatic-deductive demonstration, holding that for any results to be accepted they had to be justified in the Euclidean manner. Some traditions, both other Greek and Chinese ones especially, put greater emphasis on growing the subject, on heuristics in other words, rather than on producing incontrovertible conclusions. Why there should be such divergent aims and preoccupations and what they reflect in the values of those who pursued them are challenging questions that only really come to be visible as the questions they are when a comparative approach is adopted, though of course those comparisons extend to modern societies and do not just cover different ancient ones.

The need to do justice to all those and other differences complicates our task immeasurably. Yet it also contributes to its value – the answer to the why question. Even though the circumstances in which ancient investigators worked are so different, and in such a multitude of respects, from one another and more especially from those of today's scientists, antiquity too is worth studying for the light it can throw on the factors that stimulated and guided research or again those that inhibited it. There are ancient as well as modern examples where inquiries that originally seemed quite promising turned out to be dead ends. It is not just ancient inquirers who have deluded themselves about the prospects for understanding and control that various investigations seemed to offer. Just one of the fascinations of the study of ancient inquiries relates to how the inquirers themselves came to adopt increasingly critical attitudes to the validity of their work.

We think we have a firmer grasp, today, of what marks out what we call pseudo-sciences from the genuine ones, but that is still a topic of considerable debate, for instance in relation to which aspects of so-called alternative medicine are well grounded. One further complication is that what the usual terms for “science” cover in different modern natural languages differ. In the English-speaking world, by “science” we tend to think first and foremost of the natural sciences, what in German are called the Naturwissenschaften, which leaves German Wissenschaft free to encompass much that we would classify as learning in general.

In antiquity it is worth asking first what criteria different people appealed to in their evaluations of what is worth investigating and why. We can follow indeed how opinions on that matter changed as different inquiries battled with one another for validity, justification, and prestige. Divination was a recurrent preoccupation in most ancient societies and many different tactics were tried out. Yet in both China and Greece, in particular, some methods came to be criticized as ill-founded. Ptolemy drew a crucial distinction between prediction of the movements of the heavenly bodies themselves (astronomy, in our terms) and prediction of events on earth on their basis (astrology). The former he considered in principle a demonstrative inquiry, the latter only conjectural – yet still possible, in his view, in which he differed from other more radical Greco-Roman critics.

As regards what can promote research, the history of ancient science reveals the complex effects of state or institutional support. Sometimes that backing came at a considerable cost – as the state or political authorities concerned sought to set and control the agenda (a problem that has, of course, far from totally disappeared today). Often the growth of a subject demanded the creation of a professional elite: but those elites could and did (and still do) have negative consequences when they are intent on maintaining their own position and prestige, and resist or even stifle innovation. How lone individuals or groups came to branch out is always a difficult question, and it must still occupy our serious attention even though the history of ancient science has moved on from an earlier obsession with the genius of great heroes.

If the subject-matter we have to deal with is ancient ambitions to understand the external world, how does that history differ from history in general, and who can be expected to be interested? History in general tracks events and one of its many motivations is to try to identify causal relations and to extract general observations concerning why things happened as they did, the reasons for human successes and failures. How the physical world was to be understood takes us immediately to the beliefs that were entertained on what kind of cosmos we inhabit, to ontology in other words, and to the generally closely related assumptions about the place of humans in the scheme of things. It is not that such beliefs were static, in any ancient society. On the contrary the growth of the ambition to increase understanding generally brought with it the development of new cosmological conceptions, as well as of new ideas about values and even morality. Thus although history of science has a specific remit, that is views on the physical world, it may overlap with the work of anyone who studies the values of a given society. Although scientific research is not a branch of ethics, it may and often does implicate deep-seated values.

One such development that we can trace in antiquity was the realization, or at least the claim, that natural phenomena are marked out from the sphere of culture and of human agency and subject to their own laws and regularities. However, sometimes the contrasting assumption, that microcosm and macrocosm are interdependent and form a seamless whole was itself a powerful stimulus to investigate their purported links, analogies, and interactions. But whereas the general laws governing general history are usually highly speculative, history of science sooner or later confronts some pretty hard data. Whatever was believed about eclipses, they were there to be observed by anyone who was interested, and not only single such events, but (as we said) whole cycles of them, which we, for our part, can reconstruct using our modern knowledge. Although there are always questions concerning whether a report of some event in the sky is indeed an eclipse report, our retrospective reconstruction of the eclipses visible at any one time in any particular location enables us to verify whether an eclipse occurred at the time and the place in question. Analogously the anatomy of the human body has not changed substantially over the centuries, which means that ideas that have been entertained on that subject can be checked against modern knowledge, although of course why understanding was sought in that area is a question that has many different answers. Nevertheless while what makes humans behave in the ways they do, human nature in other words, may exhibit certain constancies if we stay at a very abstract, and not very useful, level of generalization, natural phenomena, by contrast – astronomical, optical, mechanical, zoological, botanical and the rest – manifest more impressive and robust stabilities, affording the history of that search for understanding opportunities, whether or not they were taken, to claim to have revealed the truth about those phenomena. Once again there is an overlap with later concerns, when objectivity became an increasingly contentious issue.

Is history of science, the editors ask, closer to art or to science? The question is one to which of course no simple answer can be given. Clearly the nearest we as historians get to experimentation is by entertaining thought experiments or counterfactuals and they are never subject to verification and replication. So to a scientist our reconstructions of why ancient science took the form it did may look like just so many just-so stories. Yet we obviously share with any scientist the need to check and evaluate the evidence, and when we are dealing with those hard data I spoke of, we echo the procedures of science itself. We have to exercise our imagination and sensitivity in our accounts of ancient endeavours, including of the ways in which science was written, practiced and performed, and in that respect our creativity may resemble that of any other writer or artist. Yet in another maybe more fundamental way our investigations differ from theirs, namely in the particular constraints that our evidence imposes on our interpretations.

If my arguments are accepted, the potential audience for the history of ancient science is very wide indeed, though no doubt the emphasis should be on that word “potential.” Given our current preoccupations with the prevailing ideology of science, thought of as what delivers ever-increasing material prosperity, many have little time or inclination to contemplate the varying fortunes of different ancient social, political, and institutional set-ups and their effects on research, let alone to tackle the deeper philosophical issues of the changing ontological beliefs that mark the early history of science. Yet it would be absurdly arrogant to hold that we now have unique access to the right methods, assumptions, and especially values, that should underpin scientific programs.

The value of the subject, if we do not simply turn our backs upon the past, is to throw light upon human endeavors to advance understanding of the world about us in all their manifold variety, where it was often the case that research was undertaken for what it brought the researchers by way of intellectual satisfaction, not for any practical, materialist application. In particular we can probe the conditions under which, and the limits within which, any society or any group within a society can radically challenge their own most fundamental beliefs. That, one might say, is a matter of continuing concern for anyone who seeks to make a critical appraisal of the role and future of science in our own society today. The situation of twenty-first century global science is in many respects quite unprecedented, certainly in its potential impact of the environment. But questions to do with what science is good for, to whom it should be accountable, and how it should best negotiate its independence from its paymasters (nowadays the increasingly interventionist agencies of government and industry), those questions have analogues already in much earlier periods. If we must aim at a responsible self-awareness and rid ourselves of our narrow parochialisms, our unexamined or insufficiently examined preconceptions, we need all the intellectual resources we can muster, and that certainly includes making the most of the lessons of the past.

I shall end on an autobiographical note. When I first embarked on the study of Greek science in the 1960s, at a time when little or no work was being done on that in Britain and when the great tradition of French history of science seemed moribund, I faced some pretty negative reactions from most of my senior colleagues in the general field of classical studies. I was told that if I wanted an academic career I should stick to traditional philology and edit a text: I was in the University where A.E. Housman had been Regius Professor of Greek for many years. Those who taught ancient Greek philosophy – Guthrie, Raven, Kirk, Bambrough – were less narrow-minded, but Renford Bambrough for one posited a sharp divide between the history of ancient philosophy (still useful for philosophy) and the history of ancient science (a merely antiquarian study since ancient science had been superseded). But in the still tiny department of history and philosophy of science the two leading practitioners, Mary Hesse and Gerd Buchdahl, both insisted on their interdependence, that history had much to teach philosophy but also that it needed philosophy to become self-critical.

I was lucky enough to have many other sources of inspiration, not just those two, but also the sociologically sophisticated ancient historian, Moses Finley (who edited the series in which my two handbooks on Greek science appeared) and some of the leading anthropologists of the day, Meyer Fortes, Edmund Leach, Jack Goody, later S. J. Tambiah and Alan Macfarlane. Earlier attempts by classicists – the so-called Cambridge school of Gilbert Murray, Jane Harrison and F. M. Cornford – to use anthropology had been greeted by their colleagues with a certain ambivalence. I was fortunate that in the wake of Lévi-Strauss, the anthropology practiced in Cambridge in the late 50s and 60s raised fundamental issues to do with cultural relativism and cross-cultural universals, let alone to do with la pensée sauvage, in the sharpest terms.

I take no personal credit for having combined, from the outset, history and philosophy of science, classics, and social anthropology (though, despite my friendship with Joseph Needham dating from the late 60s, it was only much later, in the late 80s that lecturing in China forced me to take seriously the need to learn classical Chinese and to appreciate what I could learn from that). All I had to do was to listen to my colleagues from different disciplines, and that also included many scientists whom I found unfailingly helpful once I engaged them with some conundrums from ancient science. What I have to thank for those connections and inspirations is simply the Collegiate structure of my University. That structure provides an inbuilt mechanism to counter the tendencies that still exist in many faculties and departments to protect their boundaries and repel boarders.

Interdisciplinarity has now become something of a buzzword, especially among those responsible for drawing up policies for Higher Education, though in some quarters it is still thought to be synonymous with superficiality. Yet to me it is clear that to study the important questions to do with human ambitions to understand the world – the different assumptions made about what counts as understanding and about what there is to be understood – we need to draw on the resources of an exceptionally wide range of different disciplines, and that is what I continue to work on and try to do today.