There is no doubt that, the first ontological cornerstone for Transcendent philosophy is seen in the "principality of Existence", according to which nothing is considered as real in the realm of existence except the being itself, and “ existence” is not realized in the mind, because it is the simple and unfolded reality whose mode of being is the refusal of “ nothingness” and being the primary source of acts or effects, and the true knowledge of existence is possible only through knowledge by presence and intuition. The question that arises here is that how beings can be perceived by presence or acquired knowledge and to what extent can such a knowledge lead us truly to knowledge? The aim of this research is to deal with this question. The concise answer is that, it is possible, to some extent, to gain knowledge of external beings by "Secondary intelligible" and "essential concepts", along with to "knowledge by presence" with all its kinds. For such concepts are abstracted from external beings and their comparison, and for the sake of this relationship, they are reflecting their own objects. In addition to "knowledge by presence" and "acquired knowledge", we also encounter creatures through senses and through this we know them. Therefore, there are various forms of knowledge of beings, and the knowledge of mankind is open to beings. However, it is worthy to note that knowing take place in a certain framework and conditions.