If you take the view that natural science and economics have nothing in common, then this is the book to read. Here, clearly, concisely and persuasively stated, are the reasons why historians of science and historians of economics share an intellectual world. Margaret Schabas's thesis is not the relatively weak one that the two fields have influenced each other (though she has plenty to say about the influence of natural philosophy on economics), but the far stronger and far more interesting one that there was originally a single field. The topics drew apart, acquiring their modern isolation from each other, she argues, only in the nineteenth century. The book should permanently alter the framework in terms of which historians think about the relations of science and economics. It is, however, restricted to English and Scottish writers, with the inevitable exception of the French physiocrats, whose work was closely connected. Quite how the British story relates to a wider picture is left unstated.

Historians have long understood that both the concept of ‘the economy’ and the discipline of economics are modern. Earlier, ‘economy’ referred to the harmony and rightness of parts within a whole; it was, for example, commonplace to refer to ‘the economy of nature’. Schabas elaborates this knowledge into the argument ‘that, until the mid-nineteenth century, economic theorists regarded the phenomena of their discourse as part of the same natural world studied by natural philosophers … Economic discourse was, in short, considered to be part of natural philosophy’. The Christian and natural-law context rendered ‘wealth … essentially a property of the physical world’ – hence the long-running assumption that wealth derives from the land. Then, over the course of the nineteenth century, Schabas argues, political economists detached the human from the natural, separating the economic sphere as the product of human choice and agency; there was a ‘denaturalization of the economic order’ (p. 2; original emphasis), above all in the work of J. S. Mill (who emerges as the pivotal figure). This denaturalization was, she implies, a central feature of a process of secularization. As a result, modern economists work in a discipline devoted to the quantitative study of ‘revealed preference’ unrelated to events ‘in nature’. The irony is not lost on Schabas that this intellectual shift occurred at the same time, and in the same context, as evolutionary theories integrated humankind into nature. She discerns little influence of evolutionary thought on the early marginalist economists. Rather, treating economic action as dependent on laws of mind, which for their purposes made human action separable from physical events, they left it to psychology to sort out ‘man's place in nature’.

The book covers sources very well known to historians of economics, if subject to diverse interpretations, in connection with which Schabas organizes what she has to say to her prime audience – the historians of science. The opening chapter, ‘Before “the economy”’, introduces the historiography using the claim that before the eighteenth century ‘there was no overarching concept of an economy’ (p. 3). She then lays out the evidence, taken from the history of natural philosophy, for the existence of a common discourse for the human and natural worlds. Subsequent chapters go more specifically into the work of the physiocrats, Hume, Smith and the classical political economists Malthus and Ricardo. The argument then turns to Mill, in whose work Schabas identifies the ‘profound departure’ (p. 19) which is crucial for her thesis. Though Mill consolidated the discipline of political economy in the terms which his predecessors had laid out, and though he added weighty philosophical authority to the principle of the uniformity of nature, Mill firmly demanded ‘that the ways of Nature are to be conquered, not obeyed’ (quoted on p. 129, from Mill's essay on ‘Nature’). The generation which followed, including W. S. Jevons and Alfred Marshall, then took it for granted that the business of the economist is like the business of the engineer, only the building materials are the psychological preferences which people show, which create the utility of material things and actions. (This ‘psychological turn’, in Schabas's words (pp. 134–41), has, it might be added, barely penetrated the consciousness of historians of psychology.) Later economists re-created ‘utility’ as an abstract function in mathematical theories of the economy.

What historians of economics will make of this is not for me to judge, but for a historian of the human sciences it is enlightening; it is also provocative, because it reverses the story conventionally told about the gradual spread of the natural sciences to encompass the human sphere. But it must be said that Schabas's preference is for the study of influences, and of the interpretative debate in the secondary sources, rather than conceptual analysis on the large scale, though her claims certainly invite the latter. Thus, at times, she makes it too easy for the casual reader to think that her concern is merely with the influence of the natural sciences on political economy. Yet there is also here a large thesis, that the contemporary belief in unlimited wealth – that is, unlimited ‘mental satisfaction or utility’ (p. 124) – became possible only with the freeing of human agency from what earlier political economists believed was its place in ‘the economy of nature’. This is, I think, an argument which, tied to the historical sources which Schabas so clearly discusses, will have a long life.