The Jewel Inside Your Skull Is Learning to Be You
Learning to Be Me (1990) [pdf]
Greg Egan's 1990 story imagines a world where everyone carries a crystalline jewel in their skull, trained by microscopic spiders to mirror their thoughts until it can replace the brain entirely. The narrator wrestles with the question of identity — whether the jewel is him or merely a perfect imitation — through childhood mockery, his parents' hidden switch, and a love affair that tests what consciousness really is.
So that when I could no longer be me, the jewel could do it for me.