The "-ian" Suffix

As I've begun to write my dissertation proposal this past week, a question occurred to me on the basis of an unthought distinction I make in my paper: what separates "Foucault's concept" from a "Foucauldian concept"?  Say one finds his account of sovereignty in the eighteenth century as unsatisfactory - his account being "Foucault's concept" - and you want to elaborate, explicate and re-work the concept such that it is satisfactory or, in my words, "properly Foucauldian."  What accounts for the shift from "so-an-so's" concept to a "so-and-so-ian" concept?

Presumably the move to a "-ian" concept involves formulating it in accord with so-and-so's general method.  Hence, a "Weberian" concept would be one based upon the ideal type and making reference to the sorts of social action; a "Marxian" concept would be one based upon its relation to the mode of production and social formation; and a "Foucauldian" concept would be...?

Take Keith Michael Baker's "A Foucauldian French Revolution?" as an example:

Could there be a Foucauldian account of the French Revolution? What might it look like? An acquaintance with more wit than sympathy for these questions compared them to asking: "If Foucault had been a painter, what colors would he have used?" The skepticism is warranted. I certainly have no fully developed "Foucauldian account of the French Revolution" to offer in what follows. Nonetheless I find it intriguing, as a historian interested in the Revolution whose approach to history has also been shaped by reading Foucault, to ask how Foucault himself might have thought about it. Nor can I resist this opportunity to try out a few ideas and speculations about how one might indeed bring some of his ideas and perspectives to an exploration of the topic.

In large part, then, what follows is offered as a jeu d'esprit - a thought-experiment to see what might now be said about the French Revolution and its origins in a Foucauldian voice. But the impersonation is only partial and sometimes breaks down. [...] While imagining how some of his ideas and arguments might advance a discursive analysis of the Revolution, I have also stepped aside to criticize them at points where they seem to be inconsistent or underdeveloped in relation to that project.

It seems, then, that a "Foucauldian concept" is one that "asks how Foucault himself might have thought about it,"  one that "brings some of his ideas and perspectives to an exploration," one that is in "a Foucauldian voice," one that is a "partial impersonation," but also one that recognizes that Foucault's own discourse might be "inconsistent or underdeveloped."  He goes on to list a few other considerations: "A Foucauldian approach to the French Revolution would doubtless have been expected to look somewhat different at varying points of his career." "I would nevertheless suggest that there would be at least two essential requirements of a Foucauldian account of the French Revolution: first, an identification of a specific technology of power; second, a genealogical  or 'eventalized' analysis of the appearance of that phenomenon." With respect to the first, "a Foucauldian approach to the French Revolution would surely be a disenchanted one" and, with respect to the second, "It required what might be called a technology of transparison, or making transparent."

However, according to Alan Apperley in an essay called "Foucault and the Problem of Method," the problem with associating Foucault with a particular method is that "Michel Foucault can be all things to all people." And, worse,  "I will argue that Foucault's thoughts and comments on questions of method problematise genealogy itself sufficiently to prevent any straightforward association between Foucault and genealogy."