Among the perceptual faculties of soul, common sense has a special place. Without giving a clear picture of it, Aristotle attributes functions such as perception of common sense impressions and sense impressions by accident and recognition of aspects of distinction between objects and comprehension of feeling to this faculty. Whereas Aristotle has clearly rejected common sense alongside the five senses, Ibn Sina and his followers regard it as one of the internal senses and attribute some of soul`s functions to it. Islamic philosophers, notably Ibn Sina, by removing certain ambiguities , putting forward reasons for proving it, and by enumerating other functions for it have reinforced Aristotle`s theory. It seems that common sense at most can be regarded as a vehicle for accepting and perceiving the sense impressions or the head of external senses; it employs the senses and then perceives the sense impressions. For this reason the act of issuing any judgment should be regarded as act by soul or attributed to the faculty of thinking. Despite the fact that the subject of knowing soul from Aristotle and Ibn Sina`s point of view have always attracted the attention of various thinkers and also each for his own part has done his best it enrich this subject, nonetheless it should be said that there are still questions that can be raised about the relation and interaction between soul, external senses, common sense and faculty of thinking that can only be illustrated properly by an exact study of subjects such as sense perception, imagination and faculties of soul.