Common sense would seem to hold that if some properties of a thing were taken away from it, it would no longer be the same thing. Further, it seems to hold that this is not the case for all properties of the thing. This intuition is the basis of the distinction between essential and accidental properties of a thing. It is also the basis of the distinction between the internal and the external relations that that thing bears to other things. For if among the properties that are essential to a thing (for example, the state of Maine) are relational properties, properties whose characterization essentially involves reference to some other thing (for example, the property of being north of Boston), then we say that the relations in question (for example, the relation between Maine and Boston) are internal to that thing (Maine...