Explaining the criterion and the basis of the good and evil deeds is one of the fundamental subjects that – prior to the Muslim philosophers- in Ionia, the Greek philosophers have brought up. They had concluded that Reason is the only criterion for the distinction of such deeds, and had considered it as a backup for the eternal moral principles. But, after the emergence of Islam, the Muslim philosophers used the Reason, first for the recognition of God acts and then, for the measurement and recognition of the human deeds. In this article, Mowlavi's viewpoint will be explained with the references to the opinions of the theologians. Considering the way that Molawi has defined justice, and his admiration of reason, one could find similarities between Molawi and the rationalists, especially Matoridiyyeh. Molawi accepts things' goodness and badness. However, he thinks of God's affairs as being relative, and therefore considers religion as assistance for Reason.Molawi, sometimes, has related the deeds' vice and virtue to their results and has considered the criterion of goodness and badness as being dependable on the emergence of their influence in the human's conscience. Therefore, in Mowlavi's viewpoint, the criterion of good and bad deeds is both rational and necessary.