Members of a third group find themselves caught in the middle, agreeing that we might be better off without the term "objective reality" but thinking, too, that we could do without "social construction." They believe neither that science has a special relationship to reality nor that its pretensions need to be unmasked. The community of natural scientists is, they think, a model of intellectual rectitude, and yet its virtues -- willingness to hear the other side, to think through the issues, to examine the evidence -- have nothing to do with the fact that the objects natural scientists investigate are found rather than made. The same virtues, after all, are found among judges and classical philologists, who investigate objects that are made rather than found.

These philosophers can agree with the social constructionists that notions like "the homosexual" and "the Negro" and "the female" are best seen not as inevitable classifications of human beings but rather as inventions that have done more harm than good. But they are not sure that "X is a social construction" adds much to "talking about X is not inevitable, and there are probably better ways of talking." They see the point of Foucault's famous observation that in the nineteenth century homosexuality was "transposed from the practice of sodomy onto a kind of interior androgyny, a hermaphroditism of the soul." Foucault went on to say, "The sodomite had been a temporary aberration; the homosexual was now a species." They agree that we would have been better off with the commonsensical thought that some men prefer to have sex with other men than with the sophisticated attempt to ground this preference in a deep, dark psychopathology. But they think that the energy Foucault's disciples have put into arguing that something is a social construction would be better put into proposing some alternative social construction: a more effective and less damaging way of talking about what is going on. All our controversial ways of talking are, to be sure, choices that society has made about how to classify things. In that sense these classifications are of course socially constructed. But the interesting question is whether anybody can suggest a better classification.

IAN Hacking -- the most intellectually curious and imaginative philosopher of science now writing -- is a member of the third group. In this spirited and eminently readable book he suggests that the combatants climb down from the level of abstraction on which they debate such topics as the nature of truth, the nature of science, and the nature of rationality, and focus instead on three questions: Are the best scientific theories of our day the inevitable results of serious inquiry, or might science have taken a different turn and still had equal success in building bombs, say, or curing diseases? Do these theories tell us about the intrinsic structure of reality, or are they simply the best tools available for predicting and controlling nature? Are the longest-lasting and most frequently relied upon theories stable because they match a stable reality, or because scientists get together to keep them stable, as politicians get together to keep existing political arrangements intact? Philosophers like Latour and Kuhn, wary of the idea that reality has an intrinsic nature that scientific inquiry is destined to reveal, are inclined to say that science might have done as good a job if it had never come up with either quarks or genes. As they see it, scientific progress is like biological evolution: no particular life-form is destined to emerge, and lots of different ones might have turned out to be equally good at survival. In this view, scientific theories are tools that do a job. They do it well, but some other tools might perhaps have done the same job equally well.