Guide to Avoiding Logical Fallacies

A Politician’s Guide to Clear Thinking | Psychology Today

Introduction to critical thinking

Arguments are attempts to persuade by providing reasons (or premises or propositions) in support of a particular claim (or conclusion).

  • In a deductive or ‘truth-preserving’ argument, the conclusion follows from the premises as their logical consequence;
  • in an inductive argument, the conclusion is merely supported or suggested by the premises.

In many cases, arguments are implicit, meaning that their rational structures and their relationships are not immediately apparent, and need to be made explicit through analysis.  

In some cases, one element (or several elements) of an argument may appear to be missing because it is implicitly assumed, that is, taken for granted.

Each premise and the conclusion can be either true or false.

The argument itself can be either valid or invalid.

An argument is valid if and only if the truth of the conclusion is a logical consequence of the premises, regardless of the truth or falsity of the premises

For an inductive argument, the equivalent of soundness is cogency. An inductive argument is cogent if its premises are true and they render the truth of the conclusion probable.

Logical fallacies

A formal fallacy is an invalid type of argument like the one above: it is a deductive argument with an invalid form, and is invalid irrespective of the content of the argument.

An informal fallacy is an argument that can be identified only through an analysis of the actual content of the argument. Informal fallacies often turn on the misuse of language, for example, using a key term or phrase in an ambiguous way, with one meaning in one part of the argument and another meaning in another part of the argument (fallacy of equivocation).

Informal fallacies can also distract from the weakness of the argument, or appeal to the emotions rather than to reason. Informal fallacies are frequently although not exclusively found in inductive arguments, and can be hard to uncover.

One way to think about it is that, whereas formal fallacies are invalid, informal fallacies are unsound.

The following non-exhaustive list of formal and informal fallacies should give you a greater insight into bad arguments…

See A Politician’s Guide to Clear Thinking | Psychology Today for the full list of fallacies.

 

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