The False Promises of Logic Textbooks - How Logic Has a Much More Limited Role Than People Usually Think

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Abstract
Logic textbooks advertise that they can teach how to spot a valid argument by its logical form alone. They also boast having collections with the most basic valid argumentative forms people of flesh and blood can use in deductive matters. Think about this for a moment. These are bold statements. If they were accurate, philosophers would be in higher demand than software engineers and no one would be able to make contributions to theoretical physics without ever taking a logic class. Of course, none of that is true. Their basic argumentative forms are nowhere to be seen in real-life argumentation and people will carry on their cognitive business without ever putting their hands on a logic textbook. I believe philosophers overpromise and underdeliver due to a subtle, but profound confusion they make about their own object of study. They take metalogical principles such as hypothetical syllogism for real forms of the arguments that are used in natural language. I try to connect these principles with real-life argumentation by interpreting their ‘premises’ as background assumptions and their ‘conclusions’ as either arguments or categorical assertions. This is not enough to save face for two reasons. First, the arguer’s assumptions should count as additional premises, but they will involve numerous arguments and the resulting formal interpretation will be too cumbersome to be practical. Second, we can’t determine the validity of an argument by formal means except when the conclusion repeats the premise, the premise is contradictory or the conclusion is tautological. These limitations are usually ignored due to the prevalent but questionable assumption that conditionals are connectives and not claims to implication. But conditionals can be elegantly explained as claims to implication in a variety of modal ranges that are all classical in nature. Consequently, the substantial validity of a deductive argument can only be determined in an informal manner and requires an extensive investigation of the nature of the subject. I conclude the article with some observations about the need to rethink the role of logic, its cognitive importance, and its teaching. Logic is important because it allows us to understand the nature of logical consequence and not because it is supposed to be useful for other deductive endeavours. I also make some observations about the need to rethink informal logic. Similarly to baby logic conventions involving formal logic, the textbook fallacies have no uncontroversial corresponding examples in real-life argumentation and are better interpreted as a list of epistemic vices that any honest epistemic agent should avoid. In this sense, informal logic has been misunderstood as a poor cousin of formal logic for decades, when it should be viewed as a speciality of virtue epistemology.
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First archival date: 2020-09-18
Latest version: 15 (2021-02-21)
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