Given Locke’s views on primary and secondary qualities, it seems he is committed to there being real underlying properties in objects, the arrangement and disposition of which underlies and produces the observed properties of that object. It might be natural to think that these primary qualities provide a general system for classifying objects into classes: that we could delineate the real kinds of objects in nature by looking at what their real primary qualities were. A list of the particular qualities of some object would define that object perfectly precisely; by looking at which properties were shared or divergent between this object and others, we group the object with others in the same kind. These real kinds in nature can play several important theoretical roles. They can support real scientific understanding, including inductive inferences (iof things are of the same real kind, then observed properties of one support the inference to unobserved properties of the other); they can form the basis for our judgements about the powers and capacities of particular objects, based on the what other things of that type can do; and these real kinds can provide the meanings for general terms: the thought being that the meanings of class names are empty without real classes to which they correspond.