The next group of fallacies are fallacies of presumption: they slip in an assumption that has not been earned. Writing an argument in standard form is the best way to catch the first one.
Key idea
An argument begs the question when a premise assumes the very conclusion it is supposed to prove, often in different words. It is circular reasoning.
Why it works
A premise is supposed to be a reason you can accept before you accept the conclusion. If the premise is the conclusion in disguise, you can only accept it if you already agree, so the argument gives a doubter nothing.
Worked example: Say it in your own words
"Reading is good for you, because reading has a positive effect on people who do it."
- Restate the premise plainly: reading is good for people.
- That is the conclusion again.
Answer: Begging the question.
Worked example: A circle through trust
"Sam always tells the truth. We know this because Sam told us so, and Sam never lies."
- To trust Sam's statement, we must already believe Sam is truthful.
- That is the conclusion.
Answer: Begging the question.
Compare: "Our team will probably win, because we beat this team twice this season and their best player is out sick." These reasons are independent of the conclusion, and you can check them, so nothing is begged.
Common mistake
In everyday speech, "that begs the question" often means "that raises the question." In logic it means circular reasoning: the conclusion hides in a premise. Test: put the premise in your own words. If you get the conclusion back, the question is begged.