Logical Fallacies…

As a follow-up to a General Lesson I had with 8D, here is a little stuff about Logical Fallacies.

This post will attempt to explain the concept (as I understand it) and later ones will focus on different specific types of fallacy. Hopefully, I will be able to include some good real-world examples with video or audio clips to support the idea – it should be fun!

The first thing to say is that this is all about forming good arguments. As we go through life, we meet a lot of people who try to convince us that their point of view is worth listening to. It may be a school friend who has a plan for some mischief, a teacher who wants you to behave in a particular way or someone on the television encouraging you to support a particular campaign. They are all presenting arguments (reasoning) and you need to be able to assess which ones to listen to and which to ignore.

There are two main kinds of argument – deductive and inductive. Deductive reasoning is more formal. Here is an example of deductive reasoning…

1. All men are mortal
2. Socrates is a man
3. Therefore Socrates is mortal

This is the classic deductive argument. If the first two lines are correct then line three must be correct. It happens that the first two lines are true so there can be no argument about the truth of the third line.

Normally we don’t get to deal with anything so cut and dried, which is where inductive reasoning joins the conversation. Take the following piece of logic as an example…

1. The Sun rises in the morning
2. The Sun has risen every previous morning
3. Therefore the Sun will rise tomorrow morning

The first two premises are correct but the conclusion does not absolutely follow. It is possible (although hugely unlikely) that something might happen to prevent the Sun rising tomorrow; it cannot be 100% ruled out so this is an inductive argument not a deductive one. It doesn’t mean it is not ‘true’, just that it is the result of induction not deduction. Most arguments you hear, and make in your writing, are inductive.

Imagine that you are writing an essay in History. The arguments you are making are based upon the evidence given in the question and your inferences drawn from what you know (or think you know) about things that happened in the past. They are almost all inductive arguments. When I complain about logical fallacies I am talking about errors in these kinds of arguments.

These fallacies/errors can be broken down into three categories. Errors of relevance, errors of ambiguity and errors of presumption.

Arguments, like ad hominem attacks or appeals to popularity, whose premises aren’t relevant to the conclusion are good examples of errors of relevance.

Straw man arguments or equivocation (my favourite!) twist the language to try to prove their point and commit errors of ambiguity.

Any argument that starts with a false or unsupported assumption commits the error of presumption. Examples include the false dichotomy and begging the question.

Over the next few weeks I will try to write a little about the logical fallacies that I most commonly notice. Hopefully it will help you to avoid being swayed by them and, equally importantly, stop you from making them yourself in your writing and debating.

I will leave you with a classic Monty Python sketch.