Begging the question (a.k.a. Circular Reasoning) is assuming as true the very thing that needs to be proven. Do you see a premise which would only be acceptable if you already believed the conclusion? Or is a premise just stating the conclusion in a different way?

Explanation:

The truth of the conclusion is assumed by the premises. Often, the conclusion is simply restated in the premises in a slightly different form. In more difficult cases, the premise is a consequence of the conclusion.

Examples:

(i) Since I'm not lying, it follows that I'm telling the truth.

(ii) We know that God exists, since the Bible says God exists. What the Bible says must be true, since God wrote it and God never lies. (Here, we must agree that God exists in orderto believe that God wrote the Bible.)

(iii) Abortion should remain legal because it is every woman's right to have one.

(iv) Abortion should become illegal because it is murder.

Proof:

Show that in order to believe that the premises are true we must already agree that the conclusion is true.