There seem to be more general philosophical questions of how anything can ever lift itself out of its own inertia and begin to change its status; whether there's an intermediate status (temporarily while the change is in progress, or perhaps permanently); and how we know when a change is complete. Or, alternatively, whether everything is always in flux, and thus questions like "What is a [fill-in-the-blank]?" don't have answers because nothing can be rigidly defined because nothing stays still. For the ancient Greeks, I think it was Zeno & Parmenides on the side of things just being what they are and Heraclitus on the side of continuous motion.
Relatedly, I've written about the sorites paradox: "Considering a pile of grain, what distinguishes a 'small heap' from a 'large heap'? No single grain makes the difference."
One way to address this for trans people asserting our genders is to say that (often) we're making a speech act wherein the words create the truth we wish to see, like casting a spell. If I'm unmarried and I say the marriage-making words at the appropriate place and time, I become a married person. Saying "I am a man" is an oath by which I adopt that gender. A 13-year-old boy at his bar mitzvah says "Today I am a man," though plainly he's not a man, he's 13, but with those words he announces his transition to adulthood, and everyone in his community agrees to see him as a man, at least in certain respects (religiously—he's allowed to lead prayer and read from the Torah). Similarly, I could join the military or change my citizenship by taking an oath.
The general idea isn't unique to gender transition. Certain features play out uniquely for trans people regarding our transitions though.
