Friday, October 28, 2016

Accretion, excretion and four-dimensionalism

Suppose we are four-dimensional. Parthood simpliciter then is an eternal relation between, typically, four-dimensional entities. My heart is a four-dimensional object that is eternally a part of me, who am another four-dimensional object.

But there is surely also such a thing as having a part at a time t. Thus, in utero my umbilical cord was a part of me, but it no longer is. What does it mean to have a part at a time? Here is the simplest thing to say:

  1. x is a part of y at t if and only if x is a part of y and both x and y exist at t.

But (1) then has a very interesting metaphysical consequence that only a few Aristotelian philosophers endorse: parts cannot survive being accreted by or excreted from the whole. For if, say, my finger survived its removal from the whole (and not just because I became a scattered object), there would be a time at which my finger would exist but wouldn’t be a part of me. And that violates (1) together with the eternality of parthood simpliciter.

This may seem to be a reductio of (1). But if we reject (1), what do we put in its place, assuming four-dimensionalism? I suspect we will have to posit a second relation of parthood, parthood-at-a-time, which is not reducible to parthood simpliciter. And that seems to be unduly complex.

So I propose that the four-dimensionalist embrace (1) and conclude to the thesis that parts cannot survive their accretion or excretion.


Michael Gonzalez said...

Well, you know me... I suggest that this is yet another reason to reject 4-dimensionalism. I have yet to see any good reasons to accept 4-dimensionalism, and I've seen very good arguments (such as those from William Lane Craig) to reject it. I mean, on 4-dimensionalism, I also have to ascribe thoughts, moral guilt and praise, etc. to proper parts of "me". It just doesn't make sense.

Alexander R Pruss said...

"I also have to ascribe thoughts, moral guilt and praise, etc. to proper parts of "me""

No, you don't. You, a four-dimensional entity, think, are guilty and praiseworthy. And you do so in a primary way. But you think different thoughts by means of different temporal aspects, just as you think different thoughts by means of different spatial aspects (say, brain hemispheres).

Michael Gonzalez said...

I have no reason to think that I think different complete thoughts in different spatial locations.... Do you have some argument that people actually do that? I'm not even sure what it means to think different thoughts by means of different "aspects".... What does that mean?

Michael Gonzalez said...

Besides consider: I don't believe for a second that my brain can have thoughts, but even if it could, it would do so by lots of things happening over the course of many milliseconds, no? If so, then no infinitesimal slice of time could have a full "thought" in it.

Nor could it be that large chunks of such slices have thoughts. That would be like having 100 brains, each of which is one of the different states along the way to having a full thought (in brain 1, neurons A and B are initializing dendrite activity; in brain 2, the neurotransmitters have begun launching across the respective synapses for A and B; in brain 3, they have arrived at the axons of neurons C and D respectively and are initiating electric response... I don't know, I'm just making this up...). Surely we shouldn't believe that there is there therefore a full thought existing among those many brains. That doesn't make any sense (even in a world where brains have thoughts at all, which, again, I deny completely).

Alexander R Pruss said...

Think of someone who had their brain hemispheres split. It sure looks like they are thinking two thoughts, each one with the help of a different half of the brain.