+Analogously, in medicine, many different pathogens can cause the same symptoms (_e.g._, coughing and sneezing), but doctors care about distinguishing different illnesses by etiology, not just symptoms, because distinct physical mechanisms give rise to distinct treatment decisions, either immediately (_e.g._, a bacterial illness will respond to antibiotics, but a viral one won't) or in principle (_e.g._, today's treatments might be equally effective against two different species of bacteria, but future drugs might work better on one or the other).
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+_As it happens_, (I claim) the evidence that gender dysphoria is more than one thing is quite stong. For reasons of personal interest, I'm going to focus on the male-to-female case for the rest of this post. An analysis of the female-to-male situation would be similar in many respects but different in others, and is left to the interested reader.
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+[explain the taxonomy, point out that it's possible to believe in a weaker version of it; link to Lawrence, &c.]
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+In less tolerant places and decades, where MtF transsexuals were very rare and had to try very hard to pass as women out of dire necessity, their impact on the social order and how people think about gender was minimal—there were just too few trans people to make much of a difference. (This is why experienced crossdressers report it being easier to pass in rural areas rather than