Formal And Informal Fallacies Pdf

formal and informal fallacies pdf

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This essay proposes and defends a general thesis concerning the nature of fallacies of reasoning. These in distinctive ways are all said to be deductively invalid.

A fallacy is simply a mistake in reasoning. Some fallacies are formal and some are informal. In Chapter 2, we saw that we could define validity formally and thus could determine whether an argument was valid or invalid without even having to know or understand what the argument was about.

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A fallacy is simply a mistake in reasoning. Some fallacies are formal and some are informal. In Chapter 2, we saw that we could define validity formally and thus could determine whether an argument was valid or invalid without even having to know or understand what the argument was about.

We saw that we could define certain valid rules of inference, such as modus ponens and modus tollens. These inference patterns are valid in virtue of their form, not their content. That is, any argument that has the same form as modus ponens or modus tollens will automatically be valid. A formal fallacy is simply an argument whose form is be invalid, regardless of the meaning of the sentences. Two formal fallacies that are similar to, but should never be confused with, modus ponens and modus tollens are denying the antecedent and affirming the consequent.

Here are the forms of those invalid inferences:. If Kant was a deontologist, then he was a non-consequentialist. Kant was not a deontologist. Therefore, Kant was a not a non-consequentialist. As you can see, this argument has the form of the fallacy, denying the antecedent. Recall our Jabberwocky argument from chapter 2.

If toves are brillig then toves are slithy. Toves are slithy 3. Therefore, toves are brillig. The point is that we can identify formal fallacies without having to know what they mean. In contrast, informal fallacies are those which cannot be identified without understanding the concepts involved in the argument.

A paradigm example of an informal fallacy is the fallacy of composition. We will consider this fallacy in the next sub-section. In the remaining subsections, we will consider a number of other informal logical fallacies. Each member on the gymnastics team weighs less than lbs.

Therefore, the whole gymnastics team weighs less than lbs. This arguments commits the composition fallacy. In the composition fallacy one argues that since each part of the whole has a certain feature, it follows that the whole has that same feature.

However, you cannot generally identify any argument that moves from statements about parts to statements about wholes as committing the composition fallacy because whether or not there is a fallacy depends on what feature we are attributing to the parts and wholes.

This conclusion does follow from the premises; there is no fallacy here. In fact both arguments have the same form:. The difference between the two arguments is not their form, but their content.

That is, the difference is what feature is being attributed to the parts and wholes. Some features like weighing a certain amount are such that if they belong to each part, then it does not follow that they belong to the whole. Other features such as being made of plastic are such that if they belong to each part, it follows that they belong to the whole. The conclusion of this argument does not follow. Contrast that example with this one:. This argument, in contrast to the last one, contains no fallacy.

It is true that if every member is on the plane then the whole team is on the plane. And yet these two arguments have almost exactly the same form.

The only difference is that the first argument is talking about the property, having been to Paris, whereas the second argument is talking about the property, being on the plane. The only reason we are able to identify the first argument as committing the composition fallacy and the second argument as not committing a fallacy is that we understand the relationship between the concepts involved.

In the first case, we understand that it is possible that every member could have been to Paris without the team ever having been; in the second case we understand that as long as every member of the team is on the plane, it has to be true that the whole team is on the plane. The take home point here is that in order to identify whether an argument has committed the composition fallacy, one must understand the concepts involved in the argument.

This is the mark of an informal fallacy: we have to rely on our understanding of the meanings of the words or concepts involved, rather than simply being able to identify the fallacy from its form.

The division fallacy is like the composition fallacy and they are easy to confuse. The difference is that the division fallacy argues that since the whole has some feature, each part must also have that feature. The composition fallacy, as we have just seen, goes in the opposite direction: since each part has some feature, the whole must have that same feature.

Here is an example of a division fallacy:. This is clearly a fallacy. The whole team died in the plane crash.

Therefore each individual on the team died in the plane crash. So this argument does not commit the division fallacy. In contrast, the following argument has exactly the same form, but does commit the division fallacy:. The team played its worst game ever tonight.

Therefore, each individual on the team played their worst game ever tonight. It can be true that the whole team played its worst game ever even if it is true that no individual on the team played their worst game ever.

This shows again that in order to identify informal fallacies like composition and division , we must rely on our understanding of the concepts involved in the argument. Capital punishment is justified for crimes such as rape and murder because it is quite legitimate and appropriate for the state to put to death someone who has committed such heinous and inhuman acts.

In standard form, the argument is this:. It is legitimate and appropriate for the state to put to death someone who commits rape or murder.

Therefore, capital punishment is justified for crimes such as rape and murder. You should notice something peculiar about this argument: the premise is essentially the same claim as the conclusion. Thus, the premise is essentially saying the same thing as the conclusion.

This is a problem: we want our premise to provide a reason for accepting the conclusion. Begging the question occurs when one either explicitly or implicitly assumes the truth of the conclusion in one or more of the premises. Begging the question is thus a kind of circular reasoning. One interesting feature of this fallacy is that formally there is nothing wrong with arguments of this form.

Here is what I mean. Consider an argument that explicitly commits the fallacy of begging the question. For example,. Capital punishment is morally permissible 2. Therefore, capital punishment is morally permissible. Now, apply any method of assessing validity to this argument and you will see that it is valid by any method. If we use the informal test by trying to imagine that the premises are true while the conclusion is false , then the argument passes the test, since any time the premise is true, the conclusion will have to be true as well since it is the exact same statement.

Likewise, the argument is valid by our formal test of validity, truth tables. But while this argument is technically valid, it is still a really bad argument. Rather, a good argument will provide some reason for accepting the conclusion that is sufficiently independent of that conclusion itself. Begging the question utterly fails to do this and this is why it counts as an informal fallacy.

What is interesting about begging the question is that there is absolutely nothing wrong with the argument formally. Whether or not an argument begs the question is not always an easy matter to sort out. As with all informal fallacies, detecting it requires a careful understanding of the meaning of the statements involved in the argument. Here is an example of an argument where it is not as clear whether there is a fallacy of begging the question:. One might think that there is a kind of circularity or begging the question involved in this argument since the argument appears to assume the truth of Christianity in justifying the claim that Christianity is true.

As this example illustrates, the issue of whether an argument begs the question requires us to draw on our general knowledge of the world. This is the mark of an informal, rather than formal, fallacy. Raising taxes on the wealthy will either hurt the economy or it will help it.

Therefore it will hurt the economy. Either raising taxes on the wealthy will hurt the economy or it will help it. Therefore, raising taxes on the wealthy will hurt the economy. In this case, the problematic disjunction is the first premise: either raising the taxes on the wealthy will hurt the economy or it will help it.

Another option is that raising taxes on the wealthy will have no effect on the economy. Notice that the argument above has the form of a disjunctive syllogism:.

Notice that the form of the argument is perfectly good—the argument is valid. False dichotomies are commonly encountered in the context of a disjunctive syllogism or constructive dilemma see chapter 2. In a speech made on April 5, , President Bush made the following remarks about the causes of the Iraq war:. Saddam Hussein once again defied the demands of the world. And so I had a choice: Do I take the word of a madman, do I trust a person who had used weapons of mass destruction on his own people, plus people in the neighborhood, or do I take the steps necessary to defend the country?

Given that choice, I will defend America every time. Other options include ongoing diplomacy and economic sanctions. That is a false dichotomy.

Informal Fallacies

A fallacy is a kind of error in reasoning. Fallacious arguments should not be persuasive, but they too often are. Fallacies may be created unintentionally, or they may be created intentionally in order to deceive other people. The vast majority of the commonly identified fallacies involve arguments, although some involve only explanations, or definitions, or other products of reasoning. The list below includes some fallacies of these sorts, but most are fallacies that involve kinds of errors made while arguing informally in natural language.


FORMAL AND INFORMAL FALLACIES. The term „fallacy‟ is ambiguous. Sometimes it refers to a mistaken belief, typically expressed as an untrue statement;.


Deductivism and the Informal Fallacies

Fallacies are mistaken beliefs based on unsound arguments. They derive from reasoning that is logically incorrect, thus undermining an argument's validity. Fallacies are difficult to classify, due to their variety in application and structure.

4.1: Formal vs. Informal Fallacies

PHIL102: Introduction to Critical Thinking and Logic

This list is based on CrossRef data as of 07 february Please note that it may not be complete. Sources presented here have been supplied by the respective publishers. Any errors therein should be reported to them. Douglas N. Hardbound — Available Buy now.

Two competing conceptions of fallacies are that they are false but popular beliefs and that they are deceptively bad arguments. These we may distinguish as the belief and argument conceptions of fallacies. Academic writers who have given the most attention to the subject of fallacies insist on, or at least prefer, the argument conception of fallacies, but the belief conception is prevalent in popular and non-scholarly discourse.

Whether a fallacy is an error or a trick, whether it is formal or informal, its use undercuts the validity and soundness of any argument. Either the premises are untrue or the argument is invalid. Below is an example of an invalid deductive argument. Premise : All black bears are omnivores. Premise : All raccoons are omnivores. Conclusion : All raccoons are black bears. Bears are a subset of omnivores.


For instance, Neuman () gave participants several types of informal reasoning fallacies, such as the argument from ignorance. This fallacy involves.


Ethics of Fallacy Detection

Abrami, P. Instructional interventions affecting critical thinking skills and dispositions: A stage I meta-analysis. Review of Educational Research, 78, 4, Aikin, S. A modest defense of fallacy theory. In Bondy, P. Alagozlu, N.

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Lola W.

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Abstract : A fallacy is a mistake in reasoning: an argument which either does not prove, or does not provide evidence for, its conclusion.

Florismart B.

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SUMMAry. Formal and informal fallacies refer to errors in reasoning or logic, which result from invalid arguments. Formal fallacies refer to arguments that have an.

Josh N.

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Formal fallacies are created when the relationship between premises and conclusion does not hold up or when premises are unsound; informal fallacies are more.

Jake C.

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Request PDF | On Jan 1, , Olatunji Alabi Oyeshile published Formal and Informal Fallacies | Find, read and cite all the research you need on.

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