7. Resisting persuasion

Analysing the validity of deductive arguments can be very useful. However, arguments can take many forms. We have seen three already: deductive, inductive, and argument from authority. Moreover, any given text often combines two or more forms of argument, and it is important to be aware of the competing demands mixed arguments make on the critical reader. The very best persuasive writers try to pummel their readers into submission with simultaneous assaults on several levels. The good critical reader needs to pull the different strategies apart and weigh them individually, resisting the temptation to be convinced by nothing other than sheer weight and variety of the assault.

As we have said, a claim that depends entirely on an argument from authority should be treated with caution, since you cannot weigh the argument yourself, you have to trust the authority. Moreover, whether the premises support the claim or not is more difficult with inductive arguments. Deciding whether an inductive argument supports the claim is a skill that you can only acquire with practice. It requires, amongst other things, the ability to imagine other possible explanations that would account for the evidence equally as well as the claim being offered.

In this post and the ones that will shortly follow, you will find a mixture of inductive, deductive and arguments from authority from a variety of sources, not just purely philosophical ones. Consider each carefully, and try to answer the questions. Here’s is the first. Study the answer key and explanatory notes before moving on to the next argument.

For the argument presented below, say what type of argument it is (deductive, inductive, argument from authority or a combination) and identify the claim. Then say WHY you think the premises either support or do not support the conclusion.

Exercise 7

Pythagoras proved that the squares on the two sides of a right-angled triangle are equal to the square on the hypotenuse. This can be seen by considering the figure below.

Square 1 and square 2 contain four triangles altogether. The large square 3 (top right), is the square on the hypotenuse c. It is the same size as the large square 4 (bottom left), which also contains four triangles. Therefore, the square on the hypotenuse c, is equal to the squares of the other two sides, a and b. Pythagoras sums this up in his famous equation, a2 + b2 = c2.

Type of argument: ___________________________________________
Claim: ________________________________________________________

It is a good/bad argument because _____________________________

When you’re done, you can check the surprising answer here. 🙂

Alternatively, continue reading the book…

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