Why can positive statements end with a negative question and vice versa?

Question

I had a hard time phrasing the actual question title—hopefully this doesn't mean it's too subjective—, but I'm curious about why positive (or negative) statements can be terminated by negative (or positive) questions:

• You do like apples, don't you?
• We can't all be rich, can we?

Why is it (arguably) common to turn a general statement into a question like this when the intent remains the same? Is this a common use of a rhetorical question? If so, what is afforded by not simply making a statement without turning it into a question?

Answer 1

As a rhetorical device, I argue that it is a leading question.

... a leading question is a question that suggests the answer or contains the information the examiner is looking for.

In law, a leading question should be avoided. I don't think that is necessarily true in informal (or even formal?) writing.

Answer 2

It is offering your conversational partner(s) a chance to contradict your current opinion. A (somewhat) polite version of "Prove me wrong" / "Am I right?"

Answer 3

The question tag comes in two flavors, contradictory and affirmative.

You like movies, don't you?

You like movies, do you?

The first is contradictory, asking for information to be polite (in case you were about to show a movie and wanted to make sure your friend wouldn't object) or because you assumed something and wanted to make sure your impression was correct.

The second is affirmative, but is also checking. The speaker has some evidence that the friend likes movies, and is asking for affirmation to confirm the supposition.

In both cases, the question tag is an invitation to confirm or deny an impression or assumption.

Answer 4

Sometimes its a simple way to formulate a yes/no question: Yes, or no? I see it as related to the practice in Romance languages of adding ¿no? to the end of a statement to make a question.

If the answer is already assumed, though, its more of a rhetorical device known as aporia. Its a technique often used in examination of witnesses by lawyers in court. ie. "You were there when the crime was committed, weren't you?"

Answer 5

You do like apples, don't you?

The sentence is used to ask somebody confirmation of the fact he/she likes apples. Who is speaking/writing thinks the other person like apples.

Depending on the context, the usage of such sentences could have different meanings.

You aren't guilty, are you?

Who is asking is not really sure the other person is not guilty, but he takes the assumption he is not.

You know who I am, don't you?

Who is speaking is reminding to the other person who he is.

Answer 6

It is reverse psychology to make the person you are talking to say what you want even if he/she isn't thinking this way. It is a proved "how to make people say yes" technique.