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Humanities LibreTexts

4.5: Common Invalid Arguments

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  • An argument is invalid when the premises do not logically lead to the conclusion. Many objections to cases against animals are of a common invalid argument form called “denying the antecedent,” where the premises do not lead to the conclusion or the conclusion logically follow from the premises. This argument is invalid:

    1. If conscious, sentient animals have moral rights then seriously harming them is typically wrong.
    2. But animals do not have any moral rights.
    3. Therefore, animal experimentation is morally permissible.

    This argument is of the same invalid pattern as this argument:

    1. If you (the reader) were a professional basketball player, then you would be over a foot tall. [TRUE!]
    2. But you are not a professional basketball player. [TRUE!?]
    3. Therefore, you are not over a foot tall. [FALSE]

    Non-professional basketball players should see that these premises are true but the conclusion false: this means that the premises do not lead to the conclusion. The same is true about the first argument above since the pattern is the same. The point applies to this invalid argument too:

    1. If animals are “equal” to humans, as “important” has humans, have the same “moral status” as humans, then seriously harming them is typically wrong.
    2. But animals are not “equal” to humans, not as “important” has humans, and do have the same “moral status” as humans.
    3. Therefore, seriously harming them is not typically wrong.

    Furthermore, what it means to say these things about “equality,” “importance,” and “moral status” are not at all clear: much explanation would be needed for the kind of understanding needed to decide whether this claim is true or false.

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