Some relevant fallacies

In this section we consider the following fallacies:

• Fallacious appeal to authority
• Fallacy of majority belief
• Appeal to tradition

Fallacious appeal to authority

If someone says you should believe something because an expert says it is true, and any of the three conditions mentioned above for a legitimate appeal to authority are not met, then you have a fallacious appeal to authority.

The fallacy of majority belief

A fallacy of majority belief occurs when someone uses the fact that most people believe something as justification for why that thing is true.

The reason this is fallacious is that it is perfectly possible for most people to believe something that is false. So, when most people believed that the world was flat, that didn’t make it flat. It is just that most people believed something which was false. And when most people believed that slavery was justifiable, that didn’t show that slavery was right. It just means that most people were wrong.

It is much harder, of course, to see that most people are wrong when sitting within that consensus. What we can do is acknowledge that this general pattern of argument fails. Any argument that appeals to widespread belief as its justification for a claim commits a fallacy of majority belief.

Consider this argument:

P1) Most people in my hometown agree that the earth is less than 10,000 years old.
                                                
C) The earth is less than 10,000 years old.

In order to make such an argument valid, the connecting premise would need to say something like

P2) If most people is my hometown agree on a thing, then that thing is true.

It’s that connecting premise, often omitted from the argument, which is false.

That example is an easy one to spot. Many examples of the majority belief fallacy are more subtle. Consider this argument.

A recent poll showed that 77% of New Zealanders support the legalisation of the medical use of cannabis. Medical cannabis should be legalised.

Reconstructed, the argument looks like this:

P1) 77% of New Zealanders support the legalisation of medical cannabis.
P2) If 77% of New Zealanders support something, then New Zealand should do that thing.
                                                
C) New Zealand should legalise medical use of cannabis.

We have a tendency to support P2: we might feel, for instance, that democracy requires that we do what most people want. But P2 is false. There are all sorts of thing that would be a bad idea to do even if 77% of New Zealanders thought it was a good idea. You might be able to get 77% of New Zealanders to agree that they should all be given a million dollars. But doing so would generate real problems.

Often, of course, the majority of people will believe something that is true. What the fallacy of majority belief brings out is that the fact that most people believe something is not, by itself, a reason to accept that something is true. You should look for other reasons.

Appeal to tradition

Appeals to tradition are like appeals to majority belief except that rather than appealing to the number of people who believe something as a reason to believe it, they appeal to how long people have believed it.

Here’s an example:

People have believed that there is a God or Gods for thousands of years – so it must be true that there is a God or Gods.  

You can probably immediately see that the objections to arguments from majority belief apply here, too. The mere fact that some belief has been around for a long time is not enough reason for you to adopt it. Instead, consider what reasons those thousands of years of humans had for believing in God, and see whether or not they were good reasons. If so, then it’s those substantial reasons that are doing the work of supporting your belief in God, not the fact that people have been believing in God for thousands of years.