are instituted among men, deriving their just powers from the consent of the governed." In a time when women, having no vote, could neither give nor withhold consent, Jefferson had to be using the word men in its principal sense of males, and it probably never occurred to him that anyone would think otherwise. For reasons like those above, supporters of gender-neutral language argue that linguistic clarity as well as equality would be better served by having man and men refer unambiguously to males, and human(s) or people to all persons; similarly, the word mankind replaced by humankind or humanity. The use of the word man as a generic word referring to all humans has been declining, particularly among female speakers and writers. Pronouns Another target of frequent criticism by proponents of gender-neutral language is the use of the masculine pronoun he (and its derived forms him, his and himself) to refer to antecedents of indeterminate gender. Although this usage is traditional, some critics argue that it was invented and propagated by males, whose explicit goal was the linguistic representation of male superiority. The use of the generic he was approved in an Act of Parliament, the Interpretation Act 1850 (the provision continues in the Interpretation Act 1978, although this states equally that the feminine includes the masculine). On the other hand, in 1879 the word "he" in by-laws was used to block admission of women to the Massachusetts Medical Society. Proposed alternatives to the generic he include he or she (or she or he), s/he, or the use of singular they. Each of these alternatives has met with objections. The use of he or she has been criticized for reinforcing the gender binary. Some feel the use of singular they to be a grammatical error, but according to most references, they, their and them have long been grammatically acceptable as gender-neutral singular pronouns in English, having been used in the singular continuously since the Middle Ages, including by a number of prominent authors, such as Geoffrey Chaucer, William Shakespeare, and Jane Austen. Linguist Steven Pinker goes further and argues that traditional grammar proscriptions regarding the use of singular "they" are themselves incorrect: Some style guides (e.g. APA) accept singular they as grammatically correct, while others reject it. Some, such as The Chicago Manual of Style, hold a neutral position on the issue, and contend that any approach used is