Human beings, and English speakers in particular, are interested in persons, not their temporal parts. Normally, that is. Fredlet can, with careful conscious effort on Fred’s part, make a statement about Fredlet, but normally he doesn’t.

My cards on the table, for what it’s worth: I see the 4D “vs” 3D “dispute” as a non-issue. Tomayto, tomahto.

Guy: Thanks for these remarks. I don’t think I disagree with them. However, with respect to your remark that “it’s doubtful that ‘I’ refers to any such present self”, Stone argues that under 4D it would (see below in my reply to Rebecca).

It strikes me that the most obvious way to reject this argument is to reject s4 (‘What it is for a person to have a thought is for a spatial part of the person (such as the brain) to have that thought’): we probably want to say something like, it’s true that it is in virtue of having a certain spatial part that a person has a thought, or that the spatial part in question plays a central role in the causal story of how that person came to have that thought; but when we talk about persons having thoughts, we are not using a shorthand for talk of their spatial parts having thoughts. A defender of 4D might say something similar, along the lines of: if we think that ‘Fred has a thought’ is a shorthand way of saying ‘Fredlet has a thought’, we misunderstand the way in which temporal parts of persons relate to persons.

First, although if persons had temporal parts these would be obvious candidates for being temporally located selves, I don’t suppose you mean to argue that if the 4D view is false, then the very idea of such selves is incoherent. This surely doesn’t follow since there might be other ways of understanding the relations between selves and persons.

Second, turning to the normative questions you briefly mention, we should distinguish questions about self-interest and claims about rationality. But I don’t think we need to talk about temporal parts to raise these questions. It’s fairly easy to raise them in terms of a person’s present desires or interests, asking whether he has reasons to fulfil his (predicted) future desires, or to care about his future interests. It’s true that talk about a person’s present interests (as opposed to talk about present desires) is not part of everyday discourse, and may be incoherent, but I don’t think the question of its coherence is decided, or even much illuminated, but this debate in metaphysics.

There is one way in which there might be a direct connection between these debates. If we allow ourselves to talk about past, present and future selves, we might find it easier to raise the question, ‘why should I, the present self, care now about my future self?’, seeing it as parallel to the question why I should care about the interests of other people. The implicit assumption here is that the normativity of self-interest is self-evident, so if I’m really a present slice of self, there’s no problem explaining why I should care about my present self, but a very genuine problem explaining why I should care about my future self. But this is a highly misleading of raising these questions, and not only because it’s doubtful that ‘I’ refers to any such present self. It’s highly misleading but, as I’ve suggested, not necessary.

On the view that only temporal parts have thoughts, Shackel/Stone would, I think, respond that Fredlet would be thinking falsely, when he thinks ‘I am a maximal space time worm.’ But, so the argument would go, this thought seems to be true. Therefore, there is something wrong with the view that only temporal parts have thoughts.

However, there are two possible moves that advocates of 4D, especially those who combine the worm view with counterpart theory (WC), could make in response. On WC, Fredlet would exist at a particular time (t); at other times (~t), only Fredlet’s counterparts would exist, if at all. So, advocates of WC could either argue that the thought ‘I am a maximal space time worm’ is actually false, if by ‘maximal space time worm,’ one means that ‘Fredlet exists at ~t.’ Or, they could argue that Fredlet is in fact thinking truly when he thinks ‘I am a maximal space time worm,’ because on a proper WC interpretation of this thought, Fredlet would be thinking that ‘Fredlet exists at t and Fredlet’s counterparts exist at ~t,’ when Fredlet is thinking this thought, which seems to be true.