The word “fallacy” comes from the Latin “fallacia” which means “deception, deceit, trick, artifice,” however, a more specific meaning in logic (a logical fallacy) that dates back to the 1550s means “false syllogism, invalid argumentation.” One of the earliest academic discussions of logical fallacies comes from the book Elementary Lessons in Logic: Deductive and Inductive, published by MacMillian and Co. in 1872 where the modern definition of logical fallacies is used: “the modes in which, by neglecting the rules of logic, we often fall into erroneous reasoning.” Today, this basic definition is still used, and often abbreviated to just “an error in reasoning.” It is not a factual error.

In the early 1970s, two behavioral researchers, Daniel Kahneman and Amos Tversky pioneered the field of behavioral economics through their work with cognitive biases and heuristics, which like logical fallacies, deal with errors in reasoning. The main difference, however, is that logical fallacies require an argument whereas cognitive biases and heuristics (mental shortcuts) refer to our default pattern of thinking. Sometimes there is crossover. Logical fallacies can be the result of a cognitive bias, but having biases (which we all do) does not mean that we have to commit logical fallacies. Consider the bandwagon effect, a cognitive bias that demonstrates the tendency to believe things because many other people believe them. This cognitive bias can be found in the logical fallacy, appeal to popularity.


The cognitive bias is the main reason we commit this fallacy. However, if we just started working at a soup kitchen because all of our friends were working there, this wouldn’t be a logical fallacy, although the bandwagon effect would be behind our behavior. The appeal to popularity is a fallacy because it applies to an argument.

I would say that more often than not, cognitive biases do not lead to logical fallacies. This is because cognitive biases are largely unconscious processes that bypass reason, and the mere exercise of consciously evaluating an argument often causes us to counteract the bias.

In this book, we are using what is referred to as the argument conception of fallacies (Hanson, 2015). That is, what we are identifying as a “logical fallacy” goes beyond the standard conception of “fallacy” where the error in reasoning must apply to argumentation. More specifically,

1. It must be an error in reasoning, not a factual error.
2. It must be commonly applied to an argument either in the form of the argument or the interpretation of the argument.
3. It must be deceptive in that it often fools the average adult.

Therefore, we will define a logical fallacy as a concept within argumentation that commonly leads to an error in reasoning due to the deceptive nature of its presentation. Logical fallacies can comprise fallacious arguments that contain one or more non-factual errors in their form or deceptive arguments that often lead to fallacious reasoning in their evaluation.

It can be, but many readers enjoy reading it cover to cover.