 In a lecture from 1951, Brouwer lists only cases 1, 2, and 4 from the above list, adding that case 3 “obviously is reducible to the first and second cases” (Brouwer 1981A: 92). That remark emphasizes an important idealization permitted in intuitionistic mathematics: we may make the idealization that, once we have obtained a decision method for a specific proposition, we also know its outcome.