Kant put his epistemology in an overall framework so that the concepts of causality, existence, substance, necessity, etc. earn their suitable place in a philosophical study. His treatment of those issues as a priori concepts which shape all of our concepts is the most important improvement in philosophy. He argued that we can understand phenomena by these categories of concepts and emphasized the importance of these categories for every kind of epistemology that originates from experience.

Just this philosophical problem was seriously analyzed by Mulla Sadra in Iran two centuries before Kant. But his treatment was different from Kant's. He distinguished between primary and secondary levels of “the intelligibles” in philosophy and logic. Then he accounted for the meanings of concepts like causality, existence, necessity and so on as “secondarily philosophical the intelligibles”.

In this paper, I compare these two ideas with each other and ex plain their advantages and disadvantages.