An analogy to reconcile gender identity and the blank slate hypothesis - if we analogize our brains at birth to brand new cars, each with the exact same components and performance figures, then gender is simply the color that our cars are painted. A trans person is therefore simply a person with a blue-car brain in the biological body more usually associated with a red-car brain (or vice-versa). Our brains are all functionally equivalent, and gender is simply an associated property of the brain with no effect on form or function.

I don't personally agree with this line of reasoning (it fails to explain how people undergoing HRT often find themselves tending in personality to become more like the stereotype of their gender identity) but it does, in my view, hold water to an extent.