Quantum Entanglement was an argument against the completeness of quantum mechanics. https://galileo-unbound.blog/2022/11/26/a-short-history-of-quantum-entanglement/ Quantum entanglement was first described by Einstein with colleagues Podolsky and Rosen in the famous EPR paper of 1935 as an argument against the completeness of quantum mechanics .At the time, Einstein worked tirelessly to expose qualities of quantum mechanics that he hoped would be so obviously unacceptable, that everyone would have to agree with his view that quantum mechanics was not the final story. And in 1935 with Boris Podolsky and Nathan Rosen, they believed to have finally found the ultimate quantum mechanical achilles heel with a property inherent to quantum mechanics later called quantum entanglement.
