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pose, leaving false clues about deliberately, like Marryatt, you know, on the railway line. All documents, you see, which don't happen to support your point of view, thereby give themselves away as being late and untrustworthy."

"But I don't think I know any history much."

"That doesn't matter; it's quite easy to read your stuff up if you confine yourself to a particular period or a particular kind of history. For the beginner, Church history may be confidently recommended. Public interest in the subject is so small that it is very unlikely anyone will take the trouble to contradict you. If the worst comes to the worst, you can always fall back upon literary criticism, and there you are on perfectly safe ground. A man with a documentary hypothesis can defy the rudest assaults of common sense."

"How does one do that, exactly?"

"You have to start out by saying, 'This document consists of three parts. One part is genuine, one part is spurious, the third part is faked evidence put in to make the spurious stuff look as if it was genuine!' Then, you see, you are on velvet. You reject altogether the parts of the document which you don't like. Then you take the remaining part, and find that it still contains a certain sort of dross⁠—evidence which still conflicts with your theory. That dross you purge away by calling it a deliberate fake. The watch says 4.54⁠—that is proof positive that, in the first place, the murder took place at 3.54, and, in the second place, the murderer tried to pre-