The union of the intellect and the intelligible is one controversial issue of philosophy examined and proved in Sadraian philosophy. In their article, the authors do not aim to repeat the pros and cons of the intellect and the intelligible or their weak and strong points; rather, they want to pursue another approach to it. Viewing the complexity of this theory, the commentators of Sadra’s theosophy have different conceptions of the tie between the intellect and the intelligible forms and their how-union. They hold that those conceptions as to knowledge fall in three groups. Having considered knowledge as the category of quality belonging to the soul, some of them say that the union of the soul and the intelligibles is of that of substance and accident. Others who regard knowledge as an illuminative attribution argue that the soul-intelligible union is the same as that of res (thing, entity) and quasi-res. Another group holds that, in Mulla Sadra’s view, knowledge is a meta-category thing [i.e. it belongs to none of Aristotelian categories of substance or accident] whose reality is identical with the soul, and thus the soul-intelligible union is of sameness. Having examined the above three views, we came to the conclusion that the intelligible form is identical with the very soul and the sameness of the intellect and intelligible is closer to Sadra’s approach.