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I'm reading the book A Concise Introduction to Logic (12th edition), and they say that this is a deduction:

Gabriel is a wolf.
Gabriel has a tail.
Therefore, Gabriel’s tail is the tail of a wolf.

Is that correct? It is not only probable that Gabriel's tail is a wolf's tail? He may can have a cat's tail because of a transplant. This conclusion necessarily follows?

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    Yes, that is a classic deduction. It only relies on premises (definitions) and logic, not observations or any other extranea. By definition, the tail on a wolf is the tail of a wolf; the wolf possesses that tail; it is the wolf's tail, regardless of how he came by it. – Dan Bron Jun 1 '16 at 13:33
  • With "a wolf tail" it'd be induction. – Quentin Ruyant Jun 1 '16 at 14:40
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Even if it was (by transplant) "a cat's tail" (phenomenological), it would still be Gabriel's tail (i.e. the tail of Gabriel, possessive/as a predicate), and since Gabriel is a wolf, it would be the tail of a wolf, namely of Gabriel the wolf (possessive/as a predicate).

Therefore, it is a clean deduction, though perhaps a bit clumsy in the formulation.

Addition including the comment of @quen_tin: The reason why the formulation is clumsy is that the fine differences between "tail of a wolf" and "wolf tail" make the difference between deduction and induction or possibly (as this is a single occurence) even more precise: Abduction.

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    +1 for mentioning abduction. Indeed, deducting that Gabriel's tail is that of a wolf is a deduction, but saying that all wolf as the same tail as Gabriel (a wolf tail) is clearly an abduction since you are generalizing from one example. – gaborous Jun 1 '16 at 20:00
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It is a deduction, namely it's a deductive argument, put it in the standard form, although it isn't clear if it's valid and sound or not(to me it is) that doesn't mean that is not a deduction. Previous answers are trying to prove the validity and soundness of this deductive argument, but your question is, if it's a deduction, which it is.

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