Shoemaker first notes that the concept of identity is consistent with temporal change. According to some objections to the Leibnitz identity theory, if a leaf is green in the summer and brown in the fall, it is not the same leaf. This, Shoemaker argues, is an inconsistent application of the identity theory. What the theory says is if a is the same as b and a at time t has property x, then b at time t will also have property x. While a at time t+1 will have property y, and b at time t+1 will have property y. In other words, if the leaf is green in the summer, and the leaf is the same leaf as the one in the fall, then the autumn leaf in the summer, will also be green and vice-versa.
Shoemaker expands this by making use of the concept of unity relations. Thus, through the use of the table analogy, while people might be sitting at the same table as the day before, there are differences, at least temporally. What we must examine are the relations between yesterday's table and today's table; this relation that holds true for both days, are what constitute the identity of the person sitting at the table.
Turning his attention to change of composition, Shoemaker argues that identity can persist through the change of internal substance because an item is not the same as the sum of its components. When we consider the object called ``tree'', we do not think of its substance and hence do not conflate the two separate items.