JPM: If human beings are to function are rational thinkers who can engage in rational deliberation, then not only must there be a unified self at each time in a deliberative sequence, but also an identical self that endures through the rational act. Consider A. C. Ewing’s argument:
To realize the truth of any proposition or even entertain it as something meaningful the same being must be aware of its different constituents. To be aware of the validity of an argument the same being must entertain premises and conclusion; to compare two things the same being must, at least in memory, be aware of them simultaneously; and since all these processes take some time the continuous existence of literally the same entity is required. In these cases an event which consisted in the contemplating of A followed by another event which consisted in the contemplating of B is not sufficient. They must be events of contemplating that occur in the same being. If one being thought of wolves, another of eating, and another of lambs, it certainly would not mean that anybody contemplated the proposition `wolves eat lambs’…There must surely be a single being persisting through the process to grasp a proposition or inference as a whole.”
If the conclusion of a syllogism is to be grasped as a conclusion, it must be drawn from the experiences of each premise singularly and, then, together. As Ewing notes, a successive series of I-stages cannot engage in such acts; only an enduring I can. Moreover, if the rational agent who embraces the conclusion is to be regarded as intellectually responsible for his reasoning, it must be the same self at the end of the process as the self who lived through the stages of reasoning that led to drawing the conclusion. One is not responsible for the acts of others or of other person-stages. So intellectual responsibility seems to presuppose an enduring I. But on the naturalist view, I am a collection of parts such that if I gain and lose parts, I am literally a different aggregate from one moment to the next. Thus, there is no such enduring I that could serve as the unifier of rational thought on a naturalist view.