If you want to acquire my method of induction, and improve your reasoning power, you must follow my system.

First think of the one absolutely undisputed, positive fact.
You must have a starting-point, and not go wandering about in the realms of suppositions." "But there are no positive facts," she said irritably.
"You don't say so ?" he said quietly.

"Do you not call it a positive fact that the bank safe was robbed of L5000 on the evening of March 25th before 11.30 p.m." "Yes, that is all which is positive and--" "Do you not call it a positive fact," he interrupted quietly, "that the lock of the safe not being picked, it must have been opened by its own key ?" "I know that," she rejoined crossly, "and that is why every one agreed that James Fairbairn could not possibly--" "And do you not call it a positive fact, then, that James Fairbairn could not possibly, etc., etc., seeing that the glass partition door was locked from the inside; Mrs.Ireland herself let James Fairbairn into her husband's office when she saw him lying fainting before the open safe.

Of course that was a positive fact, and so was the one that proved to any thinking mind that if that safe was opened with a key, it could only have been done by a person having access to that key." "But the man in the private office--" "Exactly! the man in the private office.

Enumerate his points, if you please," said the funny creature, marking each point with one of his favourite knots.