This paper shows that Du Châtelet, departing from Leibniz and Wolff, develops the concept of ‘sufficient reasonSufficient reason’ further in two significant ways: Firstly, Du Châtelet, differently to Leibniz and Wolff, explicitly delineates the relationship between the two distinct conceptsConcept ‘causeCause’ and ‘sufficient reason’. The cause contains [contienne] the principle of the actualityActuality of a beingBeing and the sufficient reason makes the existence of whatever the causeCause brings about intelligibleIntelligible to an intelligent being [Être intelligent]. (Inst1742, §9) Secondly, Du Châtelet’s theory implies that a sufficient reason is, per definitionem, intelligible to the human beingHuman being: attributesAttribute can be determined through a sufficient reason because they are intelligibleIntelligible through their relation to the essence, and modes are intelligible through their relation to material causes. By contrast, essences are not intelligible in terms of reasons or causesCause and thus do not have a sufficient reason and can only be understood through the principlePrinciple of contradiction of contradiction. Sufficient reason, in her theory, signifies that any particular existing being is intelligible through its relation to the cause that brought it about. Hence, it is erroneous to utilize the concept of sufficient reason for something that is not intelligible in this way, such as why the essence of a being is what it is or why the world exists. Although, Du Châtelet herself still, in parts, falls victim to this error, her epistemologicalEpistemological elaboration of the conceptConcept of ‘sufficient reasonSufficient reason’ in relation to cause is a step towards invalidating the intelligibilityIntelligibility of a sufficient reason in GodGod—an inheritance from Leibniz and Wolff.