Formal knowledge or conceptual perception in the philosophy of illumination

Suhrawardi, on the basis of presence or absence of the thing for the subject, classifies the human knowledge into the knowledge by presence and the conceptual knowledge.
The foundation of the knowledge by presence is the presence of soul for itself and the basis of the conceptual knowledge is the memory of the soul from the sensible world by observing it. Suhrawardi believes that the mind is the conceptual aspect of the soul. All conceptions are known by essence or by accident. He calls them the evidential and acquired knowledge. Accordingly, he has considered the sensible concepts and observations as the most evident concepts. Suhrawardi makes a distinction between the concept or idea of the thing and the thing qua thing. Moreover, he holds that the concept of thing represents one aspect of the thing and then it should not be confused between the things as things and their concept or idea.