This article tries to study comparatively the two concepts of vice and guilt and their relationship to each other in a descriptive-analytical method and based on the main works of Thomas Aquinas and Mullah Mehdi Naraghi. For Aquinas and Naraghi, vice is the opposite of virtue. From an anthropological point of view, the concept of "vice"  indicates a kind of inner and spiritual immaturity of man, and "sin" is a practical and manifested aspect of vice and practical disobedience of Allah's commands. Sin is a bad deed and vice is a bad habit. Viciousness is the source of sin, and sin is used in religious morality and is related to disobedience to the rules, and it may happen occasionally. But vice is used in philosophical morality and is considered as an internal matter. The relationship between sin and vice is like the relationship between Sharia' law and morality. In some cases they are used interchangeably, but morality is beyond the Sharia' law. One may not commit a sin, but be vicious. Therefore, one who observes the rules of the Shari'a is not necessarily considered virtuous.