Over the last three or four decades a range of searching and challenging studies in the history of optics has appeared, from classical and medieval perspectiva; through the work of early modern scholars like Descartes, Newton and Euler; to the modern achievements of Young, Fresnel and Fraunhofer. With A History of Optics Olivier Darrigol intends to provide an account that integrates the many fruits of these rather specialized researches, aiming at a wider audience of scientists, philosophers and historians. It is a laudable ambition, for an up-to-date, synthetic introduction to this interesting subfield of history of science is indeed lacking. Darrigol focuses on the development of theories of light, the mathematico-physical accounts of the nature and properties of light and its manifestations, which in his view are the essence of optics. Accordingly, instrumental and experimental practices are treated as secondary and issues of physiology and chemistry are only mentioned in passing. This choice is quite justified if one remains aware of the risk of conceiving theoretical reflections on the nature of light as the driving force of historical development. Darrigol does not avoid this risk completely. More problematic, however, is his tendency to assess historical achievements on the basis of present-day understandings of optics. This presupposes that the exposition of an Alhacen can be judged by modern knowledge and standards. Darrigol does not take into consideration that inquirers of light in the past may have had different research agendas and epistemic conceptions, which would make the question whether they were ‘right’ rather meaningless. Recent historiography of optics has made clear that the aims and methods, the disciplinary embedding, and the societal and cultural context of the engagements with light have changed continually and drastically over the centuries. Darrigol does not take such historicizing and contextualizing into account. He does acknowledge that premodern optics was a science of vision rather than of light, but still interprets perspectiva accounts in physical terms to the extent of turning essentially conceptual entities into material ones. His history is mainly a narrative of the gradual disclosure of the true state of affairs, a traditional retrospective of the prehistory of current theories. In itself, there is nothing wrong with a story of theory development that introduces scientists to the history of their field. A detour to unfamiliar and often seemingly incomprehensible ideas and practices can help to increase conceptual and methodological understanding in the natural sciences. In my experience, students often do not know what questions and problems underlie the theories and models they have to learn. Historical reflection can help reveal the pounding heart of a scientific field. Unfortunately, A History of Optics presupposes the research agenda of modern optics without explicating what it is exactly. As a result the exposition mainly consists of an enumeration of ideas, theories and discoveries that does not really make clear what its protagonists wanted to know and why: an enumeration that is prone to criticism, for example, in the rather odd account of Kepler's optics or the somewhat messy reconstruction of Descartes (which has not benefited from John Schuster's meticulous work). And the text is marred by a considerable amount of editorial flaws in dates and names, unworthy of a renowned publisher like Oxford. The historical interpretation of developments is meagre, and is confined to the brief summaries in the conclusions to the chapters. It is clear, for example, that things got really going from the time of Laplace, when a productive interplay of experimentation and theorizing developed, but Darrigol does not try to explain how this new way of knowing came about. From the late eighteenth century, A History of Optics gets into its stride; nineteenth-century physics is clearly the author's home ground. The struggles with waves, rays and ethers yield a dynamic story of mathematical modelling and conceptual considerations. Those uninitiated in modern physics will have a hard time here, for the reader is swamped with formulae with little explanation.

The final chapter, then, is somewhat disappointing. It could have provided a nice closing chord by showing how various aspects of light, like diffraction and colour theory, reveal different perspectives on light, and corresponding models bring on inherent conceptual tensions. Instead it is a collection of loose ends with a conclusion that does not really bring the book as a whole to an overall vision. All in all, what I find primarily lacking in A History of Optics is a guiding principle that leads the reader through the fascinating history of optics. Criticisms of its Popperian model notwithstanding, in his 1967 Theories of Light A.I. Sabra did exactly that for seventeenth-century optics, providing a rationale for the quest for theoretical adequacy. And even David Park, in the far from flawless The Fire within the Eye (1997), had a central idea guiding his narrative of the nature and meaning of light from antiquity to modern times – the human wondering about what light is. In the first chapters Darrigol seems to provide such a theme with the analogy between light and sound and the way this inspired optical studies. Still, it is not worked through systematically and in the end primarily seems to function to explain the principle of interference by Young. After Fresnel the theme quickly vanishes – which is not surprising, for modern physical understandings of spectra and overtones make the comparison of sound and light very problematic. All in all, Darrigol provides an overview of the main names and ideas in optics from antiquity through the nineteenth century. Added value are recently discovered topics in the history of optics, including some interesting figures in nineteenth-century optics that Darrigol has explored himself. Alas, a new and inspiring synthesis A History of Optics is not.