Kochen-Specker theorem

Etymology
Proved by John S. Bell in 1966 and by Simon B. Kochen and Ernst Specker in 1967.

Proper noun

 * 1)  A no-go theorem that places certain constraints on the permissible types of hidden-variable theories that try to explain the apparent randomness of quantum mechanics as a deterministic model featuring hidden states. It demonstrates the impossibility of quantum-mechanical observables representing "elements of physical reality".