Needing to process a multitude of complex information in a short amount of time can lead to erroneous reasoning. When a conclusion is supported by weak or irrelevant arguments, the reasoning falls into the category called non sequitur—does not follow, or irrelevant argument.

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Election campaigns often use non sequitur sophistry such as: “Lying is harmful and immoral, and a liar (candidate Y) should not be put in charge of the state, so vote with X.” The conclusion is not logical, because no steps in the argument are shown, and those that are, are not relevant to the conclusion. The first statement is correct, the second is correct, but both are irrelevant to the conclusion. The logical conclusion to the first two statements would be: do not vote for liars. The missing step in the logically false argument is: Y is a liar, and the only honest candidate is X.

Types of non sequitur

“All people who have been baptised in a Christian church will be saved. I am baptised, therefore I will be saved.” Often the lack of arguments in favour of the conclusion does not lead to a general premise, even if it is true. In this case, the premise is not true, but the conclusion may be true. Again, this depends on the missing steps in the argument.

“Believers go to church. George doesn’t go to church, so he’s not a believer.” The denial of George’s faith does not necessarily follow as a logical conclusion of this argument. To prove that George is not a faithful man, other arguments are needed.

“Because X is right, Y is not right,” “If it is love, God does not punish.” The conclusion does not follow from the premise, and the error that results is known as a disjunctive fallacy—thinking that within a choice between two things, finding one thing true makes the other thing false.

When and why a non sequitur is used

Non sequitur errors most often occur due to lack of critical thinking, or sometimes, a lack of attention. At other times, such sophisms are deliberately constructed to mislead.

When it occurs unintentionally, an error of thought is usually the result of confusion, or unconsciously seeking to maintain a previously held belief. Our perception may change, the selection of new information may become biased, the rigours of critical analysis may decrease, and so on.

When a lack of proper reasoning is combined with the desire to impose an idea, people resort to argumentative tricks that begin from true facts or ideas which they then link to conclusions that seem correct. For this form of manipulation to be successful, all that is necessary is for those being manipulated to be uninformed, inattentive, or naive.

Differences between non sequitur and other sophisms

The “red herring” sophism, aka the irrelevant argument, is used in order to change the subject of a discussion. This logical error is similar to non sequitur. Both are constructed on the basis of arguments that are irrelevant to the conclusion. The only difference is that the irrelevant argument changes the direction of a debate, while the non sequitur continues to press towards a particular conclusion, even if irrelevant.

Here is an example that differentiates the irrelevant argument from the non sequitur: In the debate over the theory of intelligent design and that of evolution, religion is the red herring. An argument such as: “Religion is concerned with finding the meaning and significance of life, so intelligent design cannot be accepted” moves the subject from the need to evaluate the intelligent design and the theory of evolution, to an irrelevant discussion over knowledge circumscribed to religion.

Instead, an argument like “Religion is concerned with man’s relationship with God, therefore it has nothing to say about the origin of life,” is a non sequitur. The fact that religion is concerned with man’s relationship with God does not mean that it has nothing to say about the origin of life.

The difference between the non sequitur sophism and the post hoc sophism (false cause) is a sensitive one. Both reach conclusions that do not derive from their premises, but the error of post hoc argumentation is built on a false causal link: If event X is followed by another event Y, it follows that Y is caused by X. The non sequitur error occurs due to a lack of logic and relevance in the relationship between argument and conclusion.

Here is an example: “M changed his Eastern-Orthodoxy for Catholicism. The day after, he had a car accident. The accident happened because he gave up the true faith.” In this case, the conclusion does not follow from the premise, but the fact that we have no argument to consider that the accident was caused by the change of religion means that this is an example of the post hoc sophism, not a non sequitur.

All sophistry contains a non sequitur. Even if it is sometimes more difficult to notice, all errors of thought mean that arguments “do not follow”. The various reasons why they do not follow fall into one category or another.

In the article, “How to build valid arguments“, Laurenţiu Moţ shows that, in order to be valid, arguments must meet several conditions. First, premises need to be valid. Then, the hypothesis of the argument must be provable on the basis of reasons and evidence. Finally, the conclusion must derive from the argument and turn the hypothesis into a thesis. “Any statement starts from a premise, which results in a hypothesis. This hypothesis must be tested, and the results are seen in a general assertion. In turn, the latter has some reasons behind it. And those reasons are supported by some evidence.” The premise leads to hypothesis, the hypothesis leads to reasons, the reasons lead to evidence, and evidence leads to a conclusion.

Non sequitur and the art of humour

Sometimes the non sequitur argument is used to abruptly change the subject, and to give the conversation a humorous touch. It is even a figure of speech used in the theater of the absurd, and is often comical. Switching from one non sequitur to another can create a comic effect. The audience’s inability to predict the string of statements in a show, and their absurdity, often leads to laughter.

Non-sequitur humour works on the basis of surreal mechanisms, combining seemingly incongruous and disparate elements in order to confuse and surprise. This illogical effect works by freeing the audience from the dominion of rationalism and thus, through changes in images, characters, and states of affairs, the room often bursts into laughter.

Enhance your critical thinking. Read more of our articles on the topic.

Ștefăniţă Poenariu is the president of the Holistic Christian Education Association, which operates Transylvania International School.