Fun question. First thoughts: logo (the computer language), the proof of the infinitude of primes, calculus and Newtonian mechanics, general relativity, the id

Fun question. First thoughts: logo (the computer language), the proof of the infinitude of primes, calculus and Newtonian mechanics, general relativity, the idea that thinking is a learnable skill. It's interesting to me what I've learnt but which didn't make my list: most things related to programming, mathematics, and physics, including quantum mechanics. Generally speaking, most of that knowledge was more incremental.