The Annotated Turing: A Guided Tour Through Alan Turing's Historic Paper on Computability and the Turing Machine

In 1914 the German governmentasked prominent scientists and artists to sign a declaration refuting the "lies andslanders of the enemy". Hilbert could not determine whether these statementsmade about Germany were true (a rather political Entscheidung problem), so herefused to sign.

Thus, 1 is actually a function with the two bound variables f and x. Just offhand, those two variables seem like two more variables than are needed to define a simple number.