St. Jerome's criteria for authenticity (and, in parentheses, Foucault's comments)
posted by Chris Schatz
1. If among several books attributed to the author, one is inferior to the others, it must be withdrawn from the list of the author's works (the author is therefore defined as a constant level of value);
2. The same should be done if certain texts contradict the doctrine expounded in the author's other works (the author is thus defined as a field of conceptual and theoretical coherence);
3. One must also exclude works that are written in a different style, containing words and expressions not ordinarily found in the writer's production (the author is here conceived as a stylistic unity);
4. Finally, passages quoting statements that were made or mentioning events that occurred after the author's death must be regarded as interpolated texts (the author is seen here as a historical figure at the crossroads of a certain number of events).
From "What is an Author?," The Foucault Reader: page 111.