The correspondence theory of truth is one of the most ancient and important theories concerning the knowledge of truth. Muslim philosophers share the same interpretation of the above theory and consider it as the correspondence of the subject and object, which is a purely quiddative kind of correspondence. In line with early philosophers, Mulla Sadra speaks of the quiddative unity of the subject and object in relation to the discussion of mental existence and the other issues related to knowledge. The present paper intends to provide an answer to the question of how we can speak about the ontological correspondence of the subject and object in Mulla Sadra’s philosophy based on its internal capabilities. Here, through explaining some of the exclusive features and principles of his philosophy, such as his ontological view of knowledge, the distinction between knowledge and mental form, the graded unity of existence, man’s previous beings and, following it, the presential perception of phenomena the writer has tried to explicate the ontological correspondence of the subject and object. The results of the conducted research indicate that quiddative correspondence comes after ontological correspondence. In other words, if we agree with quiddative correspondence, we should initially and necessarily agree with ontological correspondence as a basis for the former.