FALLIBLE FOX

Logical Fallacies (Arguments & Claims Part 6)

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Recall that a good argument has true premises, logical connections between premises and conclusions, and meets relevant standards for critical thinking (e.g., clarity; completeness). In the previous section we looked at assessing truth claims, partly to support our ability to identify true and false premises (but also for the more general reason of aiding the the verification of claims more generally). In this section, we're interested in assessing the connection between premises and conclusions. That is, does a given conclusion follow logically from the argument's premises?

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As we encounter arguments, it's important to note that that the truth of premises has no bearing on whether they serve as a logical foundation for a conclusion (recall valid deductive arguments and strong inductive arguments from an earlier section of this module). There are many ways that there can be logical incoherence between premises and conclusions, regardless of the veracity of premises. Some of these errors in logic can be chunked into categories we refer to as logical fallacies. A logical fallacy is found where, “an argument that contains a mistake in reasoning” (Bassam et al. 2013, p. 119) or, more specifically, a logical disconnect between the premise(s) and the conclusion. A premise might, for example, completely lack relevance to the conclusion. We can refer to these as fallacies of relevance. At other times, while relevant to an argument's conclusion, the premises provide insufficient support for the conclusion. These can be called fallacies of insufficient evidence.

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Other sites do a good job of describing key fallacies. Several good starting points are linked below in "Additional Resources". This section of the Argument and Truth Claims module will briefly introduce one particular fallacy to serve as an anchor point for your exploration of fallacies.

An example: Bandwagon fallacy

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​As you read, you might have some intuitive idea of when an argument is fallacious, but may not be able to put your finger on exactly what's wrong. For instance, the following is not a good argument because the premise is irrelevant to conclusion: “Most people believe Satan exists (premise) therefore Satan is real (conclusion).” You might be able to see the problem and describe it, but it can help to give it a name. This particular kind of error is known as the bandwagon fallacy. It occurs when we erroneously use other people’s beliefs to support the truth of our conclusion. In this case, the idea that lots of people believe Satan is real is used as the reason to accept that Satan exists. However, there's no good reason for people's belief in Satan to count as evidence that Satan exists. 

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This idea that majority opinion somehow provides evidence often feels convincing. Particularly when we agree with the conclusion. So, we really have to watch out for whether we're convinced by an argument that uses it. As humans, we're designed to look to the group to help us determine what's real about the world around us. That doesn't mean that it's logical to use group opinion as evidence. This is particularly the case when we have no good reason to believe that the majority's opinion is based on accurate observations. That means, there is a big difference between deference to the opinion of credible experts and non-experts. For instance, there's a big difference between these two arguments:

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1. 97% of climate scientists agree that it's extremely likely that climate change has been caused by humans. Therefore, climate change is probably caused by humans.

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2. A survey has shown that 97% of people across Canada agree that it's extremely likely that climate change has been caused by humans. Therefore, climate change is probably caused by humans.

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​While consensus among experts on climate science provides reason for us to believe that climate change is caused by humans, the opinion of the general population does not. Consensus among legitimate experts is founded in what the science currently says—there is a clear link between the premise of consensus and the conclusion. By contrast, there is no reason to believe that the general public has done, or is able to do, the required thinking to come to a credible conclusion on this topic (note that the second of the two above example arguments is fictional—no such survey was conducted).

The value of opinion of the majority differs when the topic is something that is directly observable with our senses. While our senses can't tell us anything at all about climate change, they can tell us if it's cloudy out. So if you surveyed your neighbourhood about whether there are clouds in the sky and found that 97% of people said yes, you can be reasonably certain that there are clouds in the sky.

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We can be most caught off guard when we already believe or are motivated to believe the conclusion in the argument. When the bandwagon fallacy is used in arguments that are aligned with one's core beliefs, we're more prone to let it slip by our critical thinking defences. Look at the following two arguments. Does one seem better than the other?

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1. A survey has shown that 97% of people across Canada agree that the earth is spherical and not flat. Therefore the earth is not flat.

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2. A survey has shown that 97% of people across Canada agree that the earth is flat and not spherical. Therefore the earth is flat.

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If you had read only one of these as part of a longer article you were reading, the first one is probably more likely to slip past you as perfectly fine reasoning (it isn't!). It likely confirms what you believe and perhaps reinforces your faith in humanity. However, neither of these arguments are good ones. What the general public believes about the shape of the earth, causes of climate change, when the dinosaurs went extinct, the most effective learning strategies, etc, doesn't provide good evidence in support of conclusions on the topics. Widespread belief does not count as evidence, no matter how many people hold the view (again, except when people's reality is reflected accurately in sense experience and all people surveyed have had the requisite experience).

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The bandwagon fallacy is just one example to get you started with recognizing logical errors in the relation between conclusions and the reasons offered in support of those conclusions. Always ask whether the premises really do provide evidence to accept the conclusion or whether the premises are completely irrelevant or provide insufficient evidence.

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Below, in "Additional Resources", you'll find some places where you ca learn about specific fallacies that are important to evaluating arguments—there are tons to think about and bring into your critical thinking toolkit. The better you get at spotting them, the stronger your critical thinking will get and the less likely you'll be to use them in your own thinking and writing.

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