In the 1990's Matthew Cook served as a research assistant to Stephen Wolfram , where among other things he was directed to develop a proof showing that the Rule 110 cellular automaton is Turing-complete . Under non-disclosure until the publication of Stephen Wolfram's A New Kind of Science, Cook nevertheless presented his proof at a Santa Fe Institute conference. Subsequently, it was stricken from the published proceedings by court order. Rule 110 is an extremely simple system, and the fact that it is Turing-complete is remarkable. While some view the proof as the book's central contribution, it is notable that in the years between Cook's presentation and the book's final publication, no subsequent follow-on work was done by those who had seen or heard of the proof-likely because its significance was not clear outside of the intellectual structure for which it was developed.
