The rejection of the dichotomy of contexts and the reversal of priority between justification and the genesis of knowledge to which SSK gave rise has made of experimentation a chief issue in science studies. A move towards the experimental side of science has taken place recently within philosophy, too, with such influential works as those of Harr� and Hacking, and also those of Franklin, Galison, and Nickles all of them except Franklin sympathizers with SSK. This shift of attention has taken place in a climate of harsh criticism condemning the ironic fact that the traditional conceptualist view of science had neglected the very hallmark of science, experiments. Sociologists were also aware of the problems that philosophical theses about the "theory ladenness" of observation and the "underdetermination of theories by data" had caused for the earlier simplistic view about the nature and role of the empirical base of science.

Yet there is a difference with the sociological analysis of this topic; and it leads directly to the controversy, realism versus constructivism. For with so-called laboratory studies we have to deal with the problem, not that our view of facts depends on our previous expectations and beliefs, but that the very existence of facts depends on the processes that produce them in the laboratory. And this does not mean that nature or the world has no independent existence, nor that it has no role to play in knowledge. Yet it is not this reality which scientific knowledge relies on but the one that emerges in the laboratory. Laboratory work is indeed a labor that consists of not allowing reality to remain as it was when it arrived there. Whether mice, bacteria, or chemicals, scientists' work does not consist of passively observing them, but rather of manipulating them, and transforming them. And it does all of this with intricate instruments, apparatus, and resources which are also not taken from nature, but are themselves products of prior human activities.

The problem here, as in many of the controversial points that pit sociologists against philosophers, is the use of quotations out of context. Laboratory studies in particular and SSK in general are supposed to claim a metaphysical thesis that would deny the existence of nature, the world, independent reality; and/or to claim an epistemological thesis that would deny that such reality plays a causal role in knowledge. Around these supposed claims the controversy realism versus constructivism is built. Boyd (1992), for example, says: "Realists and constructivists differ in that the former hold, while the latter deny, that the phenomena studied by scientists exist and have the properties they do independently of our adoption of theories, conceptual frameworks or paradigms."47 But what in fact constructivists deny is that those phenomena exist and have the property they do, not independently of what scientists think, but of what scientists do with them in the laboratory.

The laboratory, thus, is not a place where scientist meets nature, and its power does not reside in allowing the conditions under which phenomena naturally occur to flow freely. Rather, "The power of a laboratory is measured by the extreme conditions it is able to create: huge accelerators of millions of electron volts; temperatures approaching absolute zero; arrays of radio-telescopes spanning kilometers; furnaces heating up to thousands of degrees; pressures exerted at thousands of atmospheres; animal quarters with thousands of rats or guinea pigs; gigantic number crunchers able to do thousands of operations per millisecond."48 Speaking of laboratory studies, Giere (1988)acknowledges: "It is undeniable that these works of Latour and Woolgar and of Knorr-Cetina capture the texture of day-to-day research in a way that few other works, be they sociological, historical or philosophical, have ever done." "Still," he adds, "for anyone trained in the natural sciences or in an analytic philosophy of science, constructivism sounds wildly implausible."

Yet Latour has an explanation for this sense of implausibility; it has at its cause a paradox of scientific activity. It has to do with the fact that, once scientific results leave the lab in the form of key pieces in scientific papers, they make no reference to the actions, agents, or resources that give birth to them in the first place. All the long, expensive, and complex processes from which the results emerge become invisible. It is a fact that the inclusion or not of references to places, people, or processes marks the status of a scientific sentence. By adding such references, the status of a sentence is undermined. By removing them, it becomes more reliable. No references at all, and it is taken as uncontroversial. It is well known that there are no scientific sentences uncontroversial in themselves, something that was highlighted by the old philosophical thesis of fallibility. It is also well known that the status of sentences can change, depending on several conditions. What sociological analysis now would show is that this variability takes the form of adding or removing references to agents, places, or processes. And this is the point; it is the lack of all reference to human activity in obtaining scientific results that makes them appear as if they were, indeed, really independent of all human action. It is in this way that the independent existence of scientific phenomena, a key thesis of the realist argument, turns out to be itself a phenomenon that results from removing all reference to the actions without which the very phenomena would not exist in the first place. So Latour (1987) claims: "[Scientific] statements are not borrowed, transformed or disputed by empty-handed lay people, but by scientists with whole laboratories behind them."

Niiniluoto (1991) distinguishes philosophical naturalization (with authors like Lakatos, Laudan, or Giere), where science appears as the paradigm of human rationality, from sociological naturalization, where "scientific beliefs have no special relationship with reason, truth and reality." But, beginning with the word, "truth," I think it is reasonable to say that this has turned out to be a very elusive claim. As for "reason," I think it is reasonable to say that now as had already happened in the '60s it depends on how "reason" and "rationality" are defined. And now, as then, what seems to be challenged is some of the interpretations of such terms. Finally, with regard to "reality," I think that Niiniluotois just plain wrong. Far from saying that scientists have no special relationship with reality, constructivists claim that scientists have a very special relationship with reality, but it is a relationship about whose nature we have no idea because its investigation was forbidden by the philosophical dichotomy of contexts.

Thus far we have spoken only of sociological constructivism. Yet constructivism is also an old philosophical thesis, at least in the sense of emphasizing the active role of the subject in the construction of knowledge. In this sense, it goes back at least to Kant. Of course, there must be important differences between SSK and Kant's view of knowledge. Yet Kant did claim that the "conditions of all possible experience are, at the same time, the conditions of possibility of the object of experience."51 Perhaps the constructivism of laboratory studies could be read, pertinently and interestingly, as a sociological/naturalistic version of Kant's claim.