A hypothesis leading to a natural law?: In late 1936 Alan Turing's paper (also proving that the Entscheidungsproblem is unsolvable) was delivered orally, but had not yet appeared in print.[27] On the other hand, Emil Post's 1936 paper had appeared and was certified independent of Turing's work.[28] Post strongly disagreed with Church's "identification" of effective computability with the λ-calculus and recursion, stating: