The 10 Commandments of Logical Fallacies

1. Thou shall not attack the person’s character, but the argument. (Ad hominem)

2. Thou shall not misrepresent or exaggerate a person’s argument in order to make them easier to attack. (Straw man fallacy)

3. Thou shall not use small numbers to represent the whole. (Hasty generalization)

4. Thou shall not argue thy position by assuming one of its premises is true. (Begging the question)

5. Thou shall not claim that because something occurred before, it must be the cause. (Post Hoc/False cause)

6. Thou shall not reduce the argument down to two possibilities. (False dichotomy)

7. Thou shall not argue that because of our ignorance, claim must be true or false. (Ad ignorantium)

8. Thou shall not select only the supporting information and ignore everything that goes against the claim. (Cherry-picking)

9. Thou shall not assume “this” follows “that” when it has no logical connection. (Non sequitur)

10. Thou shall not claim that because a premise is popular, therefore it must be true.(Bandwagon fallacy)

Which logical fallacies do you think belong on this list?

Slightly adapted from here.

Logical Fallacy Land Revisited

Last week I shared a crazy email I got from some crackpot (yes, that's a well deserved ad hominem attack there) trying to sell me noni juice.

Now, I think I can safely say that juice is good for you, to a certain extent. In many ways, it's way better to eat the whole fruit, because juice usually has a very high glycemic index since it no longer has any fiber in it, and usually has a lot of sugars that get metabolized quickly, spiking your blood sugar levels. But, most juice does have vitamins, some minerals, and antioxidants. While it's good to consume your vitamins and minerals in food, antioxidants have lately been under a lot of study, some positive, some negative. So while it's good to get them in food, it's probably not beneficial to go out of your way to consume huge amounts of them.

So noni juice, which comes from the noni tree in Southeast Asia, probably has some basic goodness to it. But it's not a miracle cure. See the above link to the wikipedia article that says that noni juice has never been proven to do much of anything and can't be sold as a medical cure for anything. It's just juice, people. Overpriced and sold as a multi-level marketing scheme.

The crazy email I shared the other day really tickled my funny bone because it was so ridiculous though. Some of you commented with great rebuttals (thank you very much!), but I thought I'd go through it myself with the name of the logical fallacy in bold after the false claim made. Here's the letter again:

I am an old guy who has lived in more places than most even visit, done more different types of things than most even consider doing, much actually less do. And I have had many more professions than most. (Appeal to Irrelevant Authority. So he's an active old guy who can't hold a job. Irrelevant)

Logical Fallacy 13: Non Sequitur

Non Sequitur means "does not follow" in Latin. When the conclusion does not necessarily follow from the premises, you've committed this logical fallacy. A logical connection is implied where none exists.

This is Part 13 in a series about Logical Fallacies. We are going through one fallacy at a time. There are many types of fallacious arguments. I’m going to try to explain them with examples then find ways to help you refute those arguments when they occur. Please comment or email if there’s a particular fallacy you want me to tackle, or if you have success with refuting an argument using a good technique you can share.

Examples:

First, here's the formula:

1. If A is true, B is true.
2. B is stated to be true.
3. Therefore, A is true.

Even if the both premises and the conclusion are true, the argument is still logically bad since the premises don't support the conclusion.

1. If I am a human, I am a mammal.
2. I am a mammal.
3. Therefore, I'm human.

Even though both the premises and the conclusion are true, the argument is still a fallacy since the premises don't support the conclusion. Non sequitur reasoning can have a true conclusion or lead to a beneficial outcome. Being fallacious means the way of getting to the conclusion is not justified but it does not necessarily mean that the conclusion is false.

Here's a common example with intelligent design: