Reason is one of the pillars and core elements of the criminal procedure. Historically, criminal justice systems are generally divided into two general categories; in the first category, the "system of legal evidence", the reason is just as mentioned in the law, and thus the judge, has no right to document his sentence to the other reason. In the second, but referred to as "the system of persuasion of the judge's conscience, " the judge, in addition to the reasons set forth in the law, can study for another reason, and even make an assessment, modification and justification of the evidence presented. Today, in most legal and judicial systems, because they are given a special place in the judiciary's knowledge and give special credibility to it, they believe that due to the facts governing each case, it is necessary to give the judge some degree of discretion In order to be able to act on the basis of the spiritual evidence, that is, the evidence which eventually leads him to realistically and may not necessarily be reasoned in the law. This approach has been more and more seriously considered by the Iranian legislator recently, with the adoption of two Islamic Penal Code and Criminal Procedure Code in 1392. In this paper, we will try to discuss and analyze this approach. To this end, consideration of the meaning and qualities of fundamental concepts such as the knowledge of the judge, the spiritual proof, the proof of spiritual proof, the relevance and the breadth of the arguments are very important and central.