One of the theoretical and practical difficulties in civil proceedings is when the defendant is required to file a counterclaim in her own defense and in what cases she can defend herself without the need to file a lawsuit. Providing a clear criterion for distinguishing between these two methods of defense is necessary because counterclaims are possible by submitting a petition, paying court fees, etc., while substantive defense does not require compliance with these requirements. The legislator has made the issue ambiguous by stating that any statement such as set-off, termination, etc. that is considered a defense is not a lawsuit and does not require litigation. For this reason, the doctrine has attempted to eliminate the ambiguity of the law and provide a clear standard for judicial practice by providing criteria such as "possibility of normal proceedings", "establishment of a new situation", "declaratory or executive nature of the defense", and " transgressing of an established legal situation". But it seems that it has failed to achieve the goal and has not been able to help the judges. After criticizing the aforementioned views, this article concludes that "the defendant's direct attack on the elements of the plaintiff's case" should be used to solve the problem.