Although [Gödel 1931] failed to proved inferential undecidability of Russell's Principia Mathematica, there is a fairly simple undecidable proposition namely,

Although [Gödel 1931] failed to proved inferential undecidability of Russell's Principia Mathematica, there is a fairly simple undecidable proposition namely, the proposition *Undecidable*≡Halt<ExpressionFromString<Natural>>[RunOne.[]] where RunOne.[]≡Eval.[SelectOne.[0]] such that SelectOne.[i:Natural]≡ExpressionFromString<Natural>.[i] *finishesFirst* SelectOne.[i+1] Eval.[anExpression] evaluates anExpression and where the expression (expression1 *finishesFirst* expression2) returns the value of whichever of the expressions expression1 and expression2 evaluation finishes first. The procedure SelectOne selects one of the expressions created from strings. For details see: https://papers.ssrn.com/abstract=3603021 https://papers.ssrn.com/abstract=3603021