Hello everyone and welcome to Improve your thinking. I’m your host Kevin Browne and today I want to talk a little about logic and how you can use it. Logic is usually defined as the science of evaluating arguments. Logic gives us a set of tools for determining whether arguments are well-reasoned and if the premises provide support for the conclusion. Logic can also help us identity flaws in our reasoning.
But, some of the lessons logic can teach us are a little counter-intuitive. So, let me begin by address five of these counter-intuitive lessons that logic teaches us. 1. An argument with true statements can be invalid. An argument is said to be valid if the premises provide necessary support for the conclusion. An argument can do this with either true or false statements depending on how they are formulated. However, just because the premises of an argument are true does not mean the argument is valid. While the argument may sound persuasive, it could be the case that the premises do not provide support for the conclusion. A good example of this is the following argument which contains all true statements but is, nevertheless, invalid: All banks are financial institutions. Chase is a financial institution. Therefore, Chase is a bank. 2. Statements can sound very different, yet mean exactly the same thing. One of the insights you can learn from categorical logic is that statements which sound entirely different are, in fact, equivalent in meaning. One of the purposes of studying categorical logic is to learn precisely this insight. Another purpose is to give you the power to simplify complex statements such as this one: Some employees who are not currently on the payroll are not ineligible for workers' benefits. Categorical logic can show that this rather unclear statement is really the same as this much simpler statement: Some of those eligible for workers' benefits are not currently on the payroll. 3. There is a mathematical-like rigor to ordinary language. Certain words in ordinary language such as "and," "or," "if...then," and "if and only if" function somewhat like the mathematical operators for addition, subtraction, multiplication, and division. What this means is that you can determine whether statements are true or false without knowing everything about the statement's content. For example, in the statement "Nixon resigned the presidency and Clinton wrote the Gettysburg Address" you can determine that this statement is false if all you know is that Clinton did not write the Gettysburg Address. Partial information can lead you to detect when statements are false (or true). 4. It is possible to evaluate an argument's merits without entirely understanding its content. This possibility exists in logic due to the previous point and the fact that we can build upon it a set of rules which allow anyone to deduce an argument's validity without reference to its content. Just as in math where you can add numbers without worrying about what the numbers reference (2+3=5 and you don't need to know what you're adding 2 of and 3 of to deduce that) you can also infer an argument's validity without worrying about the argument's reference. While this is one of the most difficult points to master in the study of logic it turns out to be a very powerful tool for the evaluation of everyday arguments. 5. Fallacies of thinking are extremely common in ordinary discourse. With all the power of logical reasoning, it is still quite common for people to be persuaded by faulty arguments. What's worse is that many of these fallacies are easy to recognize with only a little training in the very basic principles of logic. Certainly one of the reasons why fallacies of thinking are so common is because they are so effective. These fallacies in reasoning are effective in part because our brains are wired up to be persuaded in ways that are not always rational and because without some basic knowledge of logic it is easy to overlook these fallacies. In logic there are specific rules for determining whether statements like that one, called a conjunction, are true or false. And, the rules are mathematical in that you can plug in a formula and determine whether the statement is true or false based on the rule which is called a truth function. The same will hold true of disjunctions which are either or statements and conditional statements which have the form If A then B. Each has a specific math like rule for determining whether the statement is true or false. In essence it gives you a sort of x-ray vision so that you can see through the clutter of an argument to its underlying form. Once you can see the form of an argument it becomes much easier to determine whether the premises are really supporting the conclusion or not. This is where knowing a little psychology comes in very handy. Logic tends to operate on the assumption that the best arguments are ones that are based on sound principles of reason and not psychological tactics. But, the best arguments from a logical standpoint are not always the most persuasive and the most persuasive arguments are not always based on sound logical principles. This raises an interesting question. Is it possible to construct an argument that is based on sound logical principles and also be psychologically persuasive? In fact it is. I’ll be discussing some interesting insights about influence in a later episode but it is entirely possible to use both sound logical principles and psychology in a way that is genuine and not manipulative. This is a point that is often overlooked in logic textbooks where any reference to psychology usually involves its potential to be used as a tool for manipulating people into agreeing with your argument. Logic does not endorse manipulation. But, you can be persuasive without being manipulative. What I’ve come to appreciate in my own study of psychology as it relates to thinking and persuasion is that it might not be possible to be persuasive if you only appeal to sound logical principles. You might get verbal agreement with the points you’re making but you probably won’t get action. Getting people to act on your argument requires that you appeal not only to their head but also their heart. If you enjoyed this episode I hope you’ll subscribe to the podcast and visit me online at kevinkbrowne.com/ Thank you for listening and I’ll see you on the next episode.
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kevin j. brownePhilosopher | Educator Archives
July 2022
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