Part 18 of Red Herrings covers still more responses to arguments that distract from the argument rather than address it directly.
We stand, Newton observed, on the shoulders of giants, but intellectually we tend to treat them as pygmies. The practice, for example, of using leeches in medicine isn’t just medieval, it’s positively ancient, with citations going back 2,500 years. When leeching went out of fashion (the late 19th century), it was obvious in retrospect how stupid these ancients were. After all, in those days they still believed the earth was flat.
The red herring of chronological snobbery is the argument that because A is an old argument, dating back to when people believed the obviously-false B, A must therefore also be false. The fact that some ancients (though fewer than you’d suppose) believed the earth was flat doesn’t in itself constitute a valid argument against anything other ancient idea. If you want to discredit A, you have to show it’s false: the proof that B is false may be valid, but utterly beside the point.
Leeches, after all, came back into medical fashion in the 1980s. It turns out that leeches are helpful in the aftermath of microsurgeries, promoting healing by allowing fresh, oxygenated blood to reach the area. The fallacy of chronological snobbery would have led investigators away from looking at a clearly outmoded idea.