The unity among past, present, and future mental states, generated and supported over time by the same body and brain, in weak reductionism is enough to yield the notion of a numerically identical and temporally extended individual.(17) This commitment to the logical relation of numerical identity distinguishes weak from strong reductionists, who are committed only to the logical relation of qualitative similarity.
The practice of holding persons responsible at later times for what they do at earlier times presupposes that a person is a numerically identical, temporally extended entity who exists at both times.
It can then seem obvious that they are numerically identical. But just as we may decline to identify the scavenger's ship with the original ship of Theseus, we may decline to identify P2 with S1.
We can defend the view that human persons are numerically identical with their bodies, that is, with the human bodies with which they are coextensive.(10) What would provide a theoretical substructure for this long overlooked defense (and for similar treatment of other putative counterexamples to the principle of one object to a place) is an accommodating general account of the relations among objects, identity criteria, and sortals.
Even numerical identity would become indistinguishable from absolute identity, if we could not assume different numerically identical
To avoid presupposing that this cell is numerically identical with UC, let us call the unattached cell "UC." The question of immediate interest (we will return shortly to the relationship of UC* to UC) is whether UC*, unlike SC and UC, is an animal.
UC* is numerically identical across time with the attached cell UC, and therefore predates the detachment; the animal that UC* constitutes does not.