Locke on the Identity of Matter

"The appropriate criterion of identity over time depends on the kind of thing is it"


We usually ask questions about identity when some sort of change is involved. Would item I remain the same if it changed in way C or would it be different? Since change takes place over time, we can usually point, in a metaphorical way, to items at different points in time. So we can ask whether an item that exists at one time is identical with one at a different time.
Locke says that an existing thing of whatever kind always exists in some place and at some time, and no existing thing of the same kind can exist in that place at that time: "whatever exists any where at any time, excludes all of the same kind, and is there itself alone". Like he states: "
An existing thing (E1) of a particular kind (K1) exists in one particular place (P1) at one particular time (T1)" ; "No two existings things (E1 and E2) of one particular kind (K1) can exist in the one particular place (P1) at the one particular time (T1)".