Eliminate all other factors, and the one which remains must be the truth.
...when you have eliminated the impossible whatever remains, HOWEVER IMPROBABLE, must be the truth...
...while the individual man is an insoluble puzzle, in the aggregate he becomes a mathematical certainty. You can, for example, never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant. So says the statistician.