Aristotle on the other hand, ascribed some value to anger that has arisen from perceived injustice because it is useful for preventing injustice. Furthermore, the opposite of anger is a kind of insensibility, Aristotle stated. The difference in people's temperaments was generally viewed as a result of the different mix of qualities or humors people contained. Seneca held that "red-haired and red-faced people are hot-tempered because of excessive hot and dry humors". Ancient philosophers rarely refer to women's anger at all, according to Simon Kemp and K.T. Strongman perhaps because their works were not intended for women. Some of them that discuss it, such as Seneca, considered women to be more prone to anger than men.