A circular argument in which the conclusion is included in the premise.
Commonly known as circular logic, this one is a favorite of those with no evidence for their position.
“A therefore A” is the basic workings of this argument. Begging the question entails assuming the premise is true in order to justify an identical conclusion. As obvious as this seems, it can be insidiously difficult to spot.
An a simple form, one used by authoritarian parents who have no good reason for demands, one may have heard this:
“I’m right because I said I’m right.”
In a more difficult to spot form, politicians are known for making multi-step circular arguments such as:
We all know Marijuana is illegal under federal law.
And we all know that you shouldn’t violate the law.
So, if smoking pot is illegal, you shouldn’t smoke pot.
And if you shouldn’t smoke pot, it is the duty of the government to stop people from smoking it,
Which is why marijuana is illegal!
A simpler example, used to rationalize belief in the Christian god:
God exists, because the Bible is the inspired word of God, and the Bible says God exists.