The chapter introduces the concept of ordinal conditional functions (OCFs) as a dynamic theory of epistemic states, aiming to address the limitations of deterministic epistemology. The author begins by discussing the formal representation of epistemic states, distinguishing between probabilistic and deterministic approaches. The deterministic approach, which treats belief as a set of propositions, is shown to have limitations in modeling rational belief change, particularly in handling successive epistemic changes. To overcome these limitations, the author proposes the concept of OCFs, which are functions that represent the ordering of disbelief in possible worlds. OCFs are more flexible than traditional deterministic partitions, allowing for reversible and commutative epistemic changes. The author defines OCFs formally and introduces the notion of conditionalization, which is crucial for updating epistemic states based on new information. The chapter also explores the concepts of independence and conditional independence within the OCF framework, providing definitions and theorems that mirror those in probability theory. These concepts are essential for understanding the structure and dynamics of epistemic states, particularly in the context of causality. Overall, the chapter aims to provide a more robust and flexible theory of epistemic states by extending the deterministic approach to include the dynamic aspects of belief change, making it a valuable contribution to the field of formal epistemology.The chapter introduces the concept of ordinal conditional functions (OCFs) as a dynamic theory of epistemic states, aiming to address the limitations of deterministic epistemology. The author begins by discussing the formal representation of epistemic states, distinguishing between probabilistic and deterministic approaches. The deterministic approach, which treats belief as a set of propositions, is shown to have limitations in modeling rational belief change, particularly in handling successive epistemic changes. To overcome these limitations, the author proposes the concept of OCFs, which are functions that represent the ordering of disbelief in possible worlds. OCFs are more flexible than traditional deterministic partitions, allowing for reversible and commutative epistemic changes. The author defines OCFs formally and introduces the notion of conditionalization, which is crucial for updating epistemic states based on new information. The chapter also explores the concepts of independence and conditional independence within the OCF framework, providing definitions and theorems that mirror those in probability theory. These concepts are essential for understanding the structure and dynamics of epistemic states, particularly in the context of causality. Overall, the chapter aims to provide a more robust and flexible theory of epistemic states by extending the deterministic approach to include the dynamic aspects of belief change, making it a valuable contribution to the field of formal epistemology.