While naturalized epistemology has become a mainstay of analytic philosophy of science, “naturalized ontology” is not exactly a household phrase. True enough, Arthur Fine has advocated the “Natural Ontological Attitude” in discussions of scientific realism. But NOA, like most of the realism debate, is concerned with the transcendental question of the status of unobservable entities in science. That debate leaves many substantive questions concerning the ontology of science unaddressed. Are scientific classification schemes based on causal power or causal history (etiology) or both? Can there be crosscutting schemes of the same scientific domain? And if so, are such classification schemes the same as incommensurable schemes? Are there such things as natural kinds, and if so, what are their distinctive features? Are some kinds more natural than others? Are there special philosophical problems associated with social categories, because of the self-reflexive nature of such categories? Do social categories have a kind of subjectivity that categories in the natural sciences lack? These questions are mostly conspicuous by their absence in recent philosophy of science.

Ian Hacking may be thought of as one of the principal proponents of naturalized ontology in the philosophy of science. Moreover, his naturalism is historicist through and through, particularly when it comes to the social sciences, which tend to be his stalking ground in these essays. Hence the title of this collection, Historical Ontology, which Hacking admits “is not, at first sight, a happy phrase” (1). The essays in this collection were written over more than a quarter of a century (from 1973 to 1999) and cover a range of topics, from Leibniz to mistranslation and from Wittgenstein to dreaming. Though the essays range widely in subject matter, Hacking proposes two recurring themes: the uses a philosopher can make of history and the work of Michel Foucault (v). Few other philosophers of science are equally at home in the world of Bachelard and Foucault as that of Carnap and Quine, and none has done so much to advance the work of all four. In this review, I will not attempt to convey the striking breadth of scope and erudition evinced in these essays, but will try to touch on a few important ideas.

What, then, is “historical ontology”? Hacking attributes the phrase to Foucault and characterizes his own version of it as follows: “My historical ontology is concerned with objects or their effects which do not exist in any recognizable form until they are objects of scientific study” (11). To illustrate, Hacking cites a doctoral thesis by James Wong on child development, which argues that our very idea of what a child is has been formed by a scientific theory of development. Though we are not forced to conceptualize children in this way, the concept of development has become a natural and pervasive category to organize our experience of children. Moreover, this and other organizing concepts come into being through specific historical processes, whose exposition may be termed “historical ontology.” Though the example of child development does not seem to have appeared in Hacking's previous writings, the general idea has been sounded in his work for well over a decade, particularly regarding such categories as child abuse, multiple personality, “mad travelers,” and so on.

So far so Foucauldian. Hacking uses these ideas to argue that in the social sciences, the very creation of categories often changes reality in the way that it does not in the natural sciences. This is what he has called elsewhere “the looping effect of social kinds” (or “interactive kinds”): the way in which “various concepts, practices, and corresponding institutions… , at the same time disclose new possibilities for human choice and action…” (4). But Hacking emphasizes that the kinds and categories associated with his historical ontology “do present themselves as positive knowledge, the bearers of general facts and testable truths about the human condition” (24). These theses are central to his “dynamic nominalism,” which holds that the creation of categories changes social reality and brings new objects into being, but that these objects are no less real for all that.

Another idea that recurs in these essays, which also touches on the central theme of the uses of history for philosophy, has to do with what Hacking calls “styles of reasoning.” He offers only ostensive definitions of this term (which he borrows from the historian of science A.C. Crombie), for example: the hypothetical construction of analogical models, or the ordering of variety by comparison and taxonomy. A necessary condition for styles of reasoning in science is that they introduce new kinds of objects and laws, and possibly also explanations, classifications, and so on (189–190). Moreover, “they introduce new ways of being a candidate for truth or for falsehood” (190), so truth and falsity can only be judged within styles of reasoning, making them “self-authenticating” and “curiously immune to anything akin to refutation” (192). But Hacking distinguishes his own view from “constructionist” accounts of science, on the grounds that these accounts hold that there are no facts to be discovered until constructed, whereas he maintains that “if a sentence is a candidate for truth or falsehood, then by using the appropriate style of reasoning we may find out whether it is true or false” (191–192). But if that sentence is not assessable in the absence of that style of reasoning, doesn't that amount to saying that the fact that it describes is constructed by that style?

Hacking does not answer all the questions associated with these important insights, but he does promise two forthcoming studies, one about making up people and another about styles of reasoning (v). The essays in this book serve to indicate new ways in which history and philosophy can interact, particularly the history and philosophy of science. Must one do philosophy of science in this way? No, and indeed Hacking himself often does not. As he points out with some satisfaction, he has just completed an elementary textbook on probability and inductive logic in which “there is no trace of historical ontology” (25). This review has touched on only a few of the essays collected in this diverse collection. Besides the essays I have cited, there is a masterful study of Descartes and Leibniz, which traces their contrasting conceptions of truth and proof, and a review of Wittgenstein's Remarks on the Foundations of Psychology, which could serve as a useful pedagogical introduction to his work in the philosophy of mind, among a number of others.