New argument in the rebuttals

A new argument in the rebuttals is, as the name suggests, a new argument raised in a rebuttal speech (the last four speeches for Team Policy, or the last three speeches for Lincoln Douglas.) This practice is universally considered unfair and prohibited, and is functionally prohibited by NCFCA and Stoa rules.

Many teams make a habit of reminding the judge that new arguments in the rebuttals should be ignored. This reminder is usually very brief and is rarely, if ever, challenged by the other team, because the doctrine of "no new arguments in the rebuttals" is so widely accepted.

Theoretical basis
Almost all debaters and coaches agree that the round functions more smoothly when arguments must be raised in the constructives. If arguments are introduced late in the round, there is less time to fully discuss them; instead of crystallizing the Affirmative and Negative positions and clarifying the key arguments in the round, the rebuttals would be a mess of brand-new positions and responses. In some cases (such as new arguments in the 2AR), there may not be time available to respond at all.

Many also argue that teams must be allowed to ask questions about new arguments. Because the rebuttals do not have cross-examination, there is no opportunity for questioning.

New arguments vs. new responses
A clear distinction must be drawn between new arguments and new responses. The typical view is that new arguments are abusive, while new responses to previously made arguments are not. For example, if the Negative brings up a new disadvantage in the 2NR, this is a new argument and viewed as abusive. If, however, the Negative brings up a disadvantage in the 2NC, the Affirmative responds in the 1AR, and the Negative responds to the responses in the 2NR, this is not viewed as a new argument or abusive behavior.

However, introducing brand-new responses to arguments that have already been responded to may be viewed as abusive. For example, if the Negative brings up a disadvantage in the 1NC, and the Affirmative responds to it in the 2AC, it may be viewed as abusive for the Affirmative to bring up an entirely new response in the 1AR (i.e., a new response to the original argument, not a response to the Negative's counter-arguments from the Negative block.)