 But this is clearly not the case because philosophers allow that one and the same action may be brought under different descriptions depending on whether it is motivated by desire (the pursuit of pleasure), by self-interest (expediency) or by duty (the right). Because philosophical distinctions bring objects under different descriptions rather than sorting them into classes, they defy the rules which apply to the relation between genera and species in the traditional theory of classification (EPM: 31). In the traditional theory of classification, the adjacent species of a genus tend to be mutually exclusive. Natural history, for example, classifies organisms into animals and vegetables, animals into vertebrates and invertebrates, vertebrates into mammals, birds, reptiles, and so on. These adjacent species tend to capture mutually exclusive classes (the class of vertebrates is different from the class of invertebrates; the class of animals is different from the class of vegetables). While there may be some overlap between adjacent species in this type of classification (the platypus is an animal that suckles its young like a mammal and lies eggs like a bird) these cases are “exceptional and limited” (EPM: 30). Overlap of classes, on the other hand, is a “regular” feature of philosophical distinctions. (EPM: 36). Philosophical distinctions allow for complete not merely partial overlap. It is not merely the case, for example, that some actions may exemplify both the concept of expediency and that of the right (in the way in which the platypus is both a mammal and a bird or amphibians are both aquatic and terrestrial animals), but that in principle any action which falls under one species of a philosophical genus could also fall under its adjacent concept: the class of actions which instantiate the principle of expediency could therefore in principle be the very same as the class of actions which instantiate the principle of duty. Collingwood’s point when claiming that the concepts of expediency and duty overlap goes beyond the epistemic consideration that it is difficult to know a person’s motive in acting, whether they were motivated by duty or by expediency; his point is rather that a philosophical distinction is “a distinction without a difference, that is, a distinction in the concepts without a difference in the instances” (EPM: 50). To say that philosophical distinctions are “distinctions without a difference” is not derogatively to dismiss them as insignificant pedantic distinctions, but to point out that philosophically to disambiguate concepts is not the same activity as sorting things into classes. To disambiguate the concept of love from that of jealousy, (not Collingwood’s example) is not the same as sorting partners into the separate classes of loving and jealous ones. By the same token to disambiguate the conception of the good into the pleasant, the expedient, and the right is not the same as sorting actions into those performed in the pursuit of pleasure, self-interest, or duty. The distinction between the pleasant, the expedient, and the right, (as with the distinction between love and jealousy) is a distinction that philosophers would want to make even if the world were such that actions motivated by duty necessarily benefitted the agent so that the class of actions motivated by self-interest or by duty would contain the very same members. Philosophical distinctions are purely intensional distinctions to which there may correspond no difference in the class of objects falling under the concepts that philosophical analysis disambiguates.