Begging the question, sometimes known by its Latin name petitio principii (meaning assuming the initial point), is a logical fallacy in which the writer or speaker assumes the statement under examination to be true. In other words, begging the question involves using a premise to support itself. If the premise is questionable, then the argument is bad.
The most basic instances of begging the question involve rephrasing. In these examples, the statement following because just restates the initial proposition in different or abstracted terms:
Freedom of speech is important because people should be able to speak freely.
The death penalty is wrong because killing people is immoral.
Ghosts are real because I have had experiences with them myself.
The first example begs the question, Why is it important for everyone to have a voice? The second begs the question, Why is killing people, and by extension the death penalty, immoral? The third raises questions about the validity of the speaker’s experience with ghosts. Even if she believes she’d had experiences with ghosts, she still needs to prove that these experiences were real.