Bitcoin's proof-of-work is not Satoshi's invention. In 1997, Adam Back published a paper called hashcash. The proposal was a tiny computational cost attached to every email, just expensive enough to slow down spam without hurting legitimate users. The cost was a SHA-256 hash with leading zeros. The cryptographic primitive at the heart of Bitcoin mining. Adam wrote the paper, shipped the C code, and watched it get adopted by anti-spam projects, ignored by the mainstream, and then cited by reference [6] of the Bitcoin whitepaper eleven years later. Satoshi did not invent proof-of-work. Satoshi noticed that a 1997 anti-spam tool could be repurposed to run a money supply. This is what intellectual lineage looks like in the cypherpunk tradition. Wei Dai wrote b-money. Nick Szabo wrote bit gold. Hal Finney ran the first node from a wheelchair. Adam Back contributed the computational engine. None of them saw the full thing. All of them built the parts. You can buy Bitcoin without knowing any of this. You will hold it longer if you do.