Just a brief scholarly note for the benefit of anybody reading Foucault's "What is Enlightenment", contained in Paul Rabinow's edited volume, "Ethics" (volume I). The index is incomplete and does not properly cover this article within the collection.
I was attempting to use the index to source mentions of Max Weber and Horkheimer (having a vague recollection of them being mentioned in Foucault's piece) and, to my dismay, could find no indexed mention of these names in any meaningful context within the book. Not giving up (Habermas' piece "Taking Aim at the Heart of the Present: On Foucault's Lecture on Kant's What is Enlightenment" claims that Foucault situates himself within a Weberian and Horkheimerian lineage) I dug out Dits et Écrits volume IV and dug through the index there.
Low and behold, the first reference I found to Horkheimer took me straight to the first page of "Qu'est-ce que les Lumières?" I immediately wondered if the translation by Catherine Porter contained in the Rabinow volume was abridged, so I began reading side-by-side with the French. It was right there, no abridgement, just not indexed. Other mentions of Weber are indexed, just not within "What is Enlightenment?"
The lesson I have learnt: the answer is often on the first page of a piece and rather than resorting to the index, I should have greater faith in my own memory, which was correct.
The lesson publishers need to learn: an index is useless if not complete and robust. Excluding a text from proper indexing wastes my time and doesn't reflect well upon you.
In the meantime, the index within Dits et Écrits seems to be complete and I would recommend anybody working on Foucault to use the comprehensive indexing there and then match up the French to any English translation you are using.
Foucault, Michel. Dits et Écrits. Paris: Gallimard, 1994. Print.
Foucault, Michel. Ethics: Subjectivity and Truth: The Essential Works of Michael Foucault, 1954-1984. Ed. Paul Rabinow. London: Penguin, 2000. Print.
Foucault, Michel. “What is Enlightenment?.” Ethics: Subjectivity and Truth: The Essential Works of Michael Foucault, 1954-1984. London: Penguin, 2000. 303-319. Print.
Habermas, Jürgen. “Taking Aim at the Heart of the Present: On Foucault's Lecture on Kant's What is Enlightenment?.” Critique and Power: Recasting the Foucault Habermas Debate. Ed. Michael Kelly. Cambridge Mass.: MIT Press, 1994. 149-154. Print.