Book excerpt: This volume translates Brentano’s intentionality into medieval psychological and ontological discussions through Sadrian theories of sense perception and mental existence. Applying a new methodology, it reframes various parts of Sadrian theory around the problem of intentionality, which results in a refreshed reading of the philosopher Mulla Sadra. The book starts out by defining intentionality problem and discussing the historiography of Brentano’s conceptualization. It examines immateriality, content and aboutness, and sense perception. In its conclusion, the book claims that intentionality in Mulla Sadra combines ontological and psychological realities and that as a result of Sadrian monism, the intentionality, intentional object, the agent, and the reality are different versions of same reality.