Michel Foucault (1926-84) played a very great role in developing approaches to subjectivity as something that is constituted, rather than pre-existing or only one-sidedly constitutive. Despite some nontrivial issues with things he said at different times, this seems like a major contribution. In his later work, he also emphasized that people actively participate in the constitution of their own subjectivity. Foucault was not only a brilliant theorist, but often expressed his ideas in beautiful, sparkling prose.
I see his focus on the constitution of subjectivity itself as an invaluable and necessary complement to the notion of a constituting subjectivity, as exemplified by, e.g., Kantian synthesis.
Much of Foucault’s work tended to fit the common trope of a “hermeneutics of suspicion” — pointing out how liberal reforms actually implemented more efficient strategies of social control, and so on. Unlike most of the people who use this phrase, I think this sort of “suspicion” of usual assumptions can play an invaluable critical role. However, I agree it can also be taken too far.
For example, received truths may turn out to be mere prejudice, and the notion of truth itself may turn out to have been naively hypostasized in many instances. But it is going too far to say — as Foucault did on several occasions — that truth and knowledge as such are inevitably caught up in strategies of domination, or — as Nietzsche and Foucault both did — that there really is no Platonic truth. In matters like this, we need an Aristotelian mean that avoids both naivete and cynicism.
I always preferred to pay more attention to Foucault’s practical multiplication of articulable differences, distinctions, and discontinuities in his historiography than to his negative rhetoric about truth and knowledge in general. During his earlier “archaeological” period, which greatly impressed me in my youth, this multiplication of articulable differences was the positive side of his questioning of too-easy unities, identities, and continuities in history. (See also Empirical-Transcendental Doublet; Genealogy; Immediacy, Presence.)
In his later work, he developed a distinctive theory of power in society, treating it as distributed everywhere at a micro level, rather than emanating from a central authority. On a practical level, this seems to me to contain valuable lessons, although it also seems to play on an ambiguity between power as capability and power as domination. (It is easy to see that power as capability is ubiquitous, and illuminating to think of how what are really modes of control may be actualized at a micro level. But capabilities and modes of control, while they are both distributed, are two different things that cannot be just identified or assumed to have the same distribution.)
He also pointed out how control can be effectuated through the very formation and self-formation of people and things, without the overt involvement of any sort of repression or repressive apparatus. This seems like another important insight.
Foucault was much influenced by the philosopher of science Georges Canguilhem’s investigations of the concept of normality in biology and medicine, which highlighted the importance of pathology for an understanding of normality. (It also appears that within the French context, the term “normativity” has strong connotations of mere empirical “normality” and conformity, in sharp contrast to its value-oriented significance in analytic philosophy and my own usage.) Foucault himself had a sort of fascination with what sociologists call deviance, and a bit of a morbid streak that I never liked.
The discursive regularities he analyzed in his earlier work represent a kind of empirical “normality” rather than an ethical normativity. Again, these are two entirely different concepts.
In Aristotelian terms, discursive regularities fall under the domain of “art” or technique, rather than that of ethos. Technique is the canonical example of an Aristotelian means or efficient cause (not to be confused with later notions of impulse, or a scholastic act of creation). As efficient causes, Foucaultian discursive regularities operate under the mode of actuality. (Ethical normativity, by contrast, involves derived ends considered under the mode of potentiality.)
Foucault’s “archaeological” method can be seen as a specialized historiographical application of what I have been calling Aristotelian semantics, concerned with fine distinctions in the ways things actually said might be meant, as well as of Aristotelian dialectic, concerned with making the practical consequences of those distinctions explicit.