Deduction, Induction, Abduction

 In 2020, I read a certain amount by the American philosopher C.S. Peirce. Some pages of what Peirce had to say turned on induction. Now, inductive proofs were familiar from a finite math class taken long ago. But the text for the course gave it much less space than Peirce and his moderns editor did.

Eventually I remembered or misremembered a passage from Tinker, Tailor, Soldier, Spy, in which Connie Sachs reports a disagreement with Percy Alleline.  In the book, it runs as follows:

Accused me of unscientific deduction. 'Whose expression is that?' I said to him. 'It's not deduction at all,' he says, 'it's induction.' 'My dear Percy, wherever have you been learning words like that; you sound just like a beastly doctor or someone.'

Certainly her inference about the Soviet spy was induction--but why that should be disqualifying, or how induction amounts to unscientific deduction is not clear. One infers on Alleline's part a mixture of feigned and real annoyance covering a weak case.

A search for more Peirce at Second Story Books turned up the monograph You Know My Method: A Juxtaposition of Charles S. Peirce and Sherlock Holmes. I have a notion, probably not uncommon among those who have read little Holmes, that Dr. Watson is forever congratulating Holmes on brilliant deductions; though the few cases that I remember seemed not to turn on deduction at all. But Holmes himself does speak of deductions, whether or not the inferences so named really are deductive.

The book cites Holmes as disclaiming guessing (The Sign of the Four). On the other hand, it documents Peirce's interest in a "singular guessing instinct", "more commonly referred to by Peirce as Abduction or Retroduction." It also gives the story of a case in which Peirce used such guessing to recover property stolen from him in the summer of 1879. (It is possible that the details of the recovery--in his disregard for the privacy of a residence--will impress or shock the modern reader as much as his acumen in identifying the thief and recovering the goods.)

 You Know My Method is part of a "Sherlock Holmes Monograph Series". It was published by Gaslight Publication of Bloomington, Indiana, in 1980. I suppose that the intended audience is one that is fascinated by Sherlock Holmes yet prepared to read about C.S. Peirce: the overlap of those fascinated by Holmes and those wishing to read Peirce must be pretty small.