Appeal to Common Practice





The Appeal to Common Practice is a fallacy with the following structure:


Premise 1: X is commonly done.

Conclusion: Therefore, X is correct/moral/justified/reasonable, etc.


The idea behind the fallacy is that the claim that many people do X is used as “evidence” to support an action or practice. It is a fallacy because just because most people do something does not make it correct, moral, justified, or reasonable.

The Appeal to Common Practice is like and often confused with the Appeal to Belief. The main difference is that the Appeal to Common Practice appeals to what people most people do and Appeal to Belief appeals to what most people think. Belief and action can, and often do, overlap so a person could combine the fallacies in making both fallacious appeals at the same time.

The fallacy seems to gain its psychological force from the tendency to believe that what is commonly done is acceptable to do. People do, of course, take their social cues from observing what others do. Another psychological factor that might be at play is that people might think that they should be allowed to do something if other people are also doing it. In some cases, this can be a non-fallacious appeal to fair play.

An appeal to fair play, which can look like an Appeal to Common Practice, need not be a fallacy. For example, a woman working in an office might say “the men who do the same job and who have the same qualifications get paid more than I do, so it would be right for me to get paid the same.” This would not be a fallacy if there was no relevant difference between her and the men (in terms of ability, experience, hours worked, etc.). An appeal to fair play has this form:


Premise 1: It is common practice to treat people of type Y in manner X and to treat people of type Z differently.

Premise 2: There is no relevant difference between people of type Y and type Z.

Conclusion: Therefore, people of type Z should be treated in manner X, too.


This argument depends on the principle of relevant difference. On this principle two people, A and B, can be justly treated differently if and only if there is a relevant difference between them. For example, it would be right for me to assign a better grade to Sally than Dave if Sally wrote a better paper than Dave. However, it would be wrong of me to assign a better grade to Sally simply because Sally has red hair and Dave has blonde hair.

Moving away from logic and into ethics, there are moral theories in which majority acceptance of X as moral entails that X is moral. The usual example of this is moral relativism: morality is relative to the practices of a culture, which can be taken as what is common practice in that culture. If what is moral is determined by what is commonly practiced, then this argument would not be a fallacy:


Premise 1: Most people in culture C do X.

Premise 2: Moral relativism is true.

Conclusion: Therefore, X is morally correct.


This sort of relativism has some interesting consequences. For example, imagine that there are only 100 people in a culture. 60 of them do not steal or cheat and 40 do. At this time, stealing and cheating would be wrong. The next day, a natural disaster kills 30 of the 60 people who do not cheat or steal. Now it is morally correct to cheat and steal. Thus, it would be possible to change the correct morality to one’s view simply by eliminating those who disagree. There are also other types of philosophical relativism, such as relativism about beauty.


Defense: The defense against this fallacy is to determine if the justification for an action or practice consists only in the claim that it is commonly done. To avoid mistaking a request for fair play with this fallacy, be sure to check to see whether that is what is occurring. If it would be reasonable to get more philosophical, you should also consider whether the argument is being made within the context of a relativistic theory, such as ethical relativism.


Example #1:

Director Jones oversees running a state waste management program. When it is found that the program is rife with corruption, Jones says “This program has its problems, but nothing goes on in this program that doesn’t go on in all state programs.”


Example #2:

“Yeah, I know some people say that cheating on tests is wrong. But we all know that everyone does it, so it’s okay.”


Example #3:

“Sure, some people buy into that equality crap. However, we know that everyone pays women less than men. It’s okay, too. Since everyone does it, it can’t really be wrong.”


Example #4:

“There is nothing wrong with requiring multicultural classes, even at the expense of core subjects. After all, all universities and colleges are pushing multiculturalism.”


Example #5:

“Of course, our company opposes toxic masculinity, supports diversity and is going green. This is what all the enlightened companies are doing these days. And as the kids say, ‘get woke or go broke.’ Wait, did I say that last thing out loud?”

Originally appeared on A Philosopher’s Blog Read More



Aristotle’s Ethics

[Revised entry by Richard Kraut on July 2, 2022. Changes to: Main text, Bibliography] Aristotle conceives of ethical theory as...


[Revised entry by Robin S. Dillon on July 2, 2022. Changes to: Main text, Bibliography] Respect has great importance in...