 In Treatise 1.3.15, Hume states eight “rules by which to judge of causes and effects” (see the block-quote above) because it is “possible for all objects to become causes or effects to each other”. The source of these rules is ambiguous. Although they “might have been supply’d by the natural principles of our understanding” (THN 1.3.15.11), Hume provides no evidence for this. Nevertheless, Hume thinks it is “proper” to employ them in his “reasoning” (THN 1.3.15.11; 1.3.15.2). Earlier in the Treatise, he was even more adamant about the regulative character of these rules: 