8.5: Fallacy of Faulty Comparison

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Page ID: 22003

Bradley H. Dowden
California State University Sacramento

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Suppose a TV commercial shows a woman wearing Jones & Jones gardening gloves. She is finishing her Saturday rose gardening without scratched hands, while her neighbor who gardens without gloves eventually quits because of the wear and tear on her hands. The commercial ends with the comment, "Don't you wish you had Jones & Jones gardening gloves?" This commercial tries to lure you into doing some faulty reasoning. The commercial creator wants you to compare having no gloves with having Jones & Jones gloves and then to conclude that you should buy Jones & Jones gloves rather than other brands. The logical reasoner will draw another conclusion. The commercial gives some reason to believe that, for gardening, wearing gloves is better than not wearing gloves, but it gives no reason to believe that Jones & Jones gloves are better than any other brand of gloves. This commercial offers a faulty comparison. The comparison should have been between Jones & Jones gloves and competing brands of gloves, not between Jones & Jones gloves and no gloves at all. The advertising agency that created the commercial intentionally used the fallacy of faulty comparison to deceive viewers. What was compared wasn't what should have been compared.

Exercise \(\PageIndex{1}\)

Explain why the fallacy of faulty comparison occurs in the following advertisement for Flox mouthwash, and explain how to revise the ad to remove the problem:

Flox removes 300 percent more plaque than simple rinsing. Isn't that reason enough for your family to buy Flox?

Answer: The advertisement encourages you to buy Flox instead of competing mouthwashes by luring you into comparing Flox with no brushing at all. To remove the fallacy and make the point the advertiser wants to make, the Flox mouthwash should be compared with other mouthwashes. For example, the ad could say, "When compared to all other mouthwashes, Flox removes 15 percent more plaque. Isn't that reason enough for your family to buy Flox?"

Consider this ad: "Enzine detergent motor oil causes less exhaust emission than the leading seller. Buy Enzine." The faulty comparison problem can be useful for understanding this ad. Even if the ad is correct in what it says, you still need to worry before you decide to buy Enzine. For consumers to make an informed decision about which product to buy, shouldn't the Enzine oil be compared with all the other motor oils, not merely the leading seller? The best seller might be best merely because it is the most highly advertised or least expensive, not because it is a high-quality product. The second major difficulty with the ad is that Enzine might be better than all the other products in terms of exhaust emission, but what about other considerations, such as price and constancy of viscosity, that are important for motor oils? When all these factors are considered, the leading seller might be better for your engine than Enzine, even if what the ad says is true. By selectively presenting the comparison information and by not giving you the other relevant information, the ad is presenting a half-truth.