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.
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:
No one knows what caused the Big Bang.
Therefore God did it. (This is also the God of the Gaps Argument: I can't understand it so God did it.)
The creationist has the burden of proof in this argument. In order to say that God caused the Big Bang, they must first show that the universe couldn't always have existed, or come from another collapsed universe, etc. Then they have to show that science will never solve the problem. Then they have to show that their god is the cause and not some other god. Then they have to prove that their god exists. Then they have to prove that their god actually caused the Big Bang.
How to Refute A Non Sequitur Argument
The easiest way to refute this type of argument is to explain to the person how the non sequitur works. So if someone says, "If I drink this beer, I will be popular and hot girls will think I'm sexy" you can explain that it's a logical fallacy commonly used by advertisers. They show two different things (a man drinking a beer, and hot girls all over him while he drinks it) and lead you to believe that one leads to the other, when in fact they might have nothing to do with each other. He might have just won the lottery, or he might be really funny. Who knows? The girls may have bought him the beer to celebrate his promotion. It could be anything. The two things might have any type of connection, or none at all.
And remember to explain that even if there is a connection, it doesn't mean the argument is sound, as in the first example about mammals and humans.