 This account is intuitive, but perhaps it cannot be treated as a formally adequate definition of the notion of primary substance or individual. Fido the individual could be said to be in a certain location and so attributed to something, namely a place. It is natural to reply to this that an object is not an attribute of a place in the same way as a property is an attribute of a thing: the property is in a thing ‘as a subject’, but a place is not a subject to which a thing is attributed: the place does not ‘underlie’ the thing as a thing ‘underlies’ its properties. Although this may be true, it presupposes that we already have a grasp on the sense in which properties belong to objects and how this differs from the various ways that objects belong to or can be attributed to things, and that we can call upon this informal understanding in interpreting the theoretical account. Whether this is legitimate might depend on what the objective is. If the objective is to explain the difference between substance and property in an entirely non-circular way by appealing to the fact that properties are in substances but substances are not in things, this would involve taking the notion of being in as primitive. If we have to distinguish the sense in which properties are in substances from the way in which substances can be in things—such as places—before we can make the original point, then there has not been a non-circular account. If, on the other hand, the objective is simply to differentiate between concepts already in play, then Categories achieves its objective.