The issue raised in this article is primarily based on the claim of mistake and the principle of validity in contracts. The issues related to mistake have been detailed in articles of Law 199, 200 , and 201 of the Civil Laws / Codes. Article 223 of the Civil Law deals with the principle of validity and plays a significant role in raising claims / law - suits.The plaintiff's ignorance and errors always contradict the principles of validity in transactions. On the other hand, the legal presumption on erroneous transaction leads to validity. How can one make a compromise between these two principles?A)First of all, the limits of the applicability of the principle of validity, from the jurisprudents' perspectives and views, is based on two criteria:1- Its trend in all conditions and under all circumstances, verified or unverified, as determined and accepted in this paper as a general principle.2- The principle of validity in all parts and conditions, as well as unverified / unfounded conditions. B) There are differences between these two bases disregarding the validity or lack of validity of the plaintiff's errors.In the present article, this issue has been dealt with.C) The principle of validity is to be given priority regarding the principle of contradiction whether the cause to the contract is a claim of ignorance or not, whether the claim of error is a common or a civil law.This perspective is in concordant with all social interests, the solidity of contracts as well as the individuals good wills and other principles of contracts.