Question

All men are chairs. John Doe is a man. In logical language, therefore:

• A. John Doe is a chair
• B. John Doe is a human being and therefore he cannot be a chair
• C. A man cannot be a chair in any case
• D. Chairs can be men

Hint:

When faced with absurd premises in logical reasoning, follow the premises as stated for the sake of deduction, even though the conclusion may not make sense in the real world.

Answer 1

The Correct Option is A

This problem illustrates a fallacy or absurd argument where a premise is presented without any real-world basis. The statement “All men are chairs” is an absurd proposition because men cannot be chairs. However, given this flawed premise, the conclusion that “John Doe is a chair” follows logically based on the premise. Here's the reasoning:
- According to the given statement, “All men are chairs,” it asserts that every man is a chair.
- Since “John Doe is a man,” he must, by the illogical premise, also be a chair.
This conclusion is valid only if we accept the absurd premise. However, in real-world logic, this statement is nonsensical, but it is a valid conclusion based on the false premise. Therefore, the answer is (A).

Answer 2

This question tests whether we can separate logical validity from real-world truth. The premises given are "All men are chairs" and "John Doe is a man." Let's check what conclusion these premises force, then see which option matches.

1. John Doe is a chair: This follows the standard pattern of a categorical syllogism: "All A are B" (all men are chairs), "C is A" (John Doe is a man), therefore "C is B" (John Doe is a chair). The form is identical to valid syllogisms such as "All men are mortal, Socrates is a man, therefore Socrates is mortal." Since the premises are accepted as given for the purpose of the argument, the conclusion "John Doe is a chair" follows by strict logical necessity from them, however strange it sounds.
2. John Doe is a human being and therefore he cannot be a chair: This brings in outside, real-world knowledge to reject the premises, rather than working within the logical structure the question sets up. Logic problems of this type ask what follows from the premises, not whether the premises match reality, so this option abandons the given premises instead of reasoning from them.
3. A man cannot be a chair in any case: This directly contradicts the first premise, "All men are chairs", which the argument asks us to accept as given. Rejecting the premise outright is not a conclusion drawn from the argument; it is a refusal to engage with it.
4. Chairs can be men: This reverses the direction of the original premise. "All men are chairs" only tells us that the category "men" sits inside the category "chairs", not that every chair is a man. This statement is not something the premises establish.

Since the premises must be taken as given, the only option that is a genuine logical consequence of them, following the exact same valid syllogistic form used throughout formal logic, is the first one.

Therefore, the correct answer is John Doe is a chair.

Answer 3

This question tests whether we accept a given premise, even a strange one, and follow it to its necessary conclusion. Let \( M \) stand for "is a man," \( C \) stand for "is a chair," and \( j \) stand for John Doe. The two premises given are: every \( M \) is a \( C \), and \( j \) is an \( M \). Substituting \( j \) into the general rule directly gives \( j \) is a \( C \). Let's check each option against this substitution.

1. John Doe is a chair: This is exactly the result of substituting John Doe into the rule "every man is a chair." Once the premises are accepted as given, this substitution is automatic and leaves no room for a different conclusion.
2. John Doe is a human being and therefore he cannot be a chair: This brings in a fact, that John Doe is human, that isn't one of the two premises supplied. Introducing an outside fact to override the given rule means abandoning the premises rather than substituting into them.
3. A man cannot be a chair in any case: This flatly denies the first premise, "all men are chairs," rather than substituting John Doe into it. Denying a premise isn't the same as drawing a conclusion from it.
4. Chairs can be men: The premise states that the set of men sits inside the set of chairs, every man is a chair, not that every chair is a man. Substituting John Doe requires going in the direction the premise actually states, man to chair, not the reverse.

Substituting John Doe into the accepted rule produces one, and only one, result.

Therefore, the correct answer is John Doe is a chair.