Contemporary misunderstanding of the term derives from the double meaning of the word "moral" in the nineteenth century context. According to Erdmann Mueller in a comprehensive 1899 treatise on moral insanity: "the word "moral" in the concept moral insanity is derived from the word affective in Esquirol's terminology, and the translation of "moral" as virtuous or ethical is the result of a misunderstanding due to the double meaning of the word." According to Pinel, "manie sans délire" (mania without delusion) had no relation to the moral faculty. Moral insanity was a form of mental derangement in which the intellectual faculties were unaffected, but the affects or emotions were damaged, causing patients to be carried away by some kind of furious instinct ("instincte fureur").