+In my youth (when I stood on the steps of the University library, pressed the copy of _The Singularity Is Near_ fast to my chest, and pretended I was Kathy), I used to be more optimistic about the future of human enhancement. "Oh, sure, that may be true of _present-day humans_, but _in general_ ..." actually felt like a relevant and useful form of argument to me.
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+These days, I'm less likely to appeal to technologies that don't already exist. I think what changed is that as I read more and gained some personal experience with real-world technology development (albeit in mere software), I began to appreciate technology as specific, contingent developments with particular implementation details that someone had to work out, rather than as an unspecified generic force of everything getting better over time. _In principle_, everything not directly prohibited by the laws of physics is probably possible, but in practice, every capability depends on vast institutions and supply chains and knowledge that can be lost as well as gained.
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