Begging the question

by Tim Harding

Setting aside for a moment whatever personal views we might have about the morality of abortion, consider the following argument:

   Premise 1: Murder is morally wrong;

   Conclusion: Therefore, abortion is morally wrong.

Is this argument logically valid?  Probably not, but let’s analyse the form of the argument to make sure:

    Premise 1: A is B;

    Conclusion: Therefore, C is B.

An argument of this form is logically invalid, i.e. the conclusion can be false even when the premises are true.  Or in other words, the conclusion does not necessarily follow from the premises.

OK, how about this argument:

   Premise 1: Abortion is murder;

   Premise 2: Murder is morally wrong;

   Conclusion: Therefore, abortion is morally wrong.

Is this argument valid?  The form of this argument is:

   Premise 1: A is B;

   Premise 2: B is C;

   Conclusion: Therefore, A is C.

In this second case, the conclusion necessarily follows from the premises. That is, if the premises are true (which they may or may not be), then the conclusion must be true by virtue of the logical structure of the argument. So this form of this argument is logically valid. However, if one or more of the premises is false, then the conclusion may also be false (even though the argument is valid). This example also illustrates the importance difference between validity and truth.

The first argument was missing a premise, which when included, turned the argument from an invalid one to a valid one.  This is an instance of the formal fallacy known as the Fallacy of the Unstated Major Premise or ‘Begging the Question’.

The Latin name for it is petitio principia, meaning a request for the beginning or premise’.  Or in other words, this fallacy is committed when one makes an argument assuming a premise that is not explicitly stated.  It is not to be confused with the meaning of ‘raising the question’, which is sometimes mistakenly referred to as ‘begging the question’ in the popular media.

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Filed under Logical fallacies

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