Animalism without biologism

Animalism holds that we are animals. This is a pretty common-sense view. We are clearly mammals, and mammals are animals.

However, there is a common objection: cerebrum transplants. As the objection goes, if your cerebrum is transplanted from your skull to a different skull (or to a supportive vat), you follow the cerebrum, while the animal stays with the lower brain and the rest of the body. So you are not the animal.

Let me say something that will sound silly: This objection is guilty of biologism about animals. The biologism here consists in the claim that we should take how biologists think about the continuity of animal life to be normative for how we should think about the identity of animals. You might think it’s obvious that we should engage in biologism about animals. But biologists are not metaphysicians, and the question of the metaphysical identity over time of animals does not really enter into the empirical investigations biologists engage in.

On what I think is the correct metaphysics of animals, the identity of an organism over time is grounded in the persistence of the animal’s soul or form, a metaphysical feature of the animal which is largely beyond the interest of contemporary biologists. Moreover, the animal’s form is responsible for its teleological structure, which defines what the animal’s flourishing is, and what is and is not central to that flourishing. It is plausible—though not necessary—to think that the form tends to remain with those components of the animal that are more central to its flourishing as the kind of thing it is.

In the case of homo sapiens, central to its flourishing is the exercise of the excellences of intellect and will. And the cerebrum is more directly involved in these exercises than any other part of the body, so it is plausible to think that the human animal goes with the cerebrum in a transplant.

Biologistically speaking, it is tempting to think of the intellect and will as subserving the animal functions of homeostatic maintenance, growth and reproduction. But that is a mistake. In a human, the functioning of the intellect and will is more central to flourishing than the animal functions.

This may seem discontinuous from other animals. Some will be happy with the discontinuity and some will think it’s a reductio ad absurdum of the view. But I think there is less discontinuity than seems to be the case. Think of dogs. It seems that their social life, with one another and with humans, constitutes more of their flourishing than their performance of the functions that define biological life. The social life presumably evolved because it promoted nutrition, growth and reproduction, but the social life appears more valuable. Given the likely ties between this social life and the cerebrum, it would not surprise me if dogs went with their cerebra in a cerebrum transplant.

The questions here are ones of value, and we should avoid biologism about value, even in non-human animals.

Of snakes and cerebra

Suppose that you very quickly crush the head of a very long stretched-out serpent. Specifically, suppose your crushing takes less time than it takes for light to travel to the snake’s tail.

Let t be a time just after the crushing of the head.

Now causal influences propagate at most at the speed of light or less, the crushing of the head is the cause of death, and at t there wasn’t yet time for the effects of the crushing to have propagated to the tip of the tail. Furthermore, assume an Aristotelian account of life where a living thing is everywhere joined with its form or soul and death is the separation of the form from the matter. Then at t, because the effects of crushing haven’t propagated to the tail, the tail is joined with the snake’s form, even though the head is crushed and hence presumably no longer a part of the snake. (Imagine the head being annihilated for greater clarity.)

Now as long as any matter is joined to the form, the critter is alive. It follows that at time t, the snake is alive despite lacking a head. The argument generalizes. If we crush everything but the snake’s tail, including crushing all the major organs of the snake, the snake is alive despite lacking all the major organs, and having but a tail (or part of a tail).

So what? Well, one of the most compelling arguments against animalism—the view that people are animals—is that:

1. People can survive as just a cerebrum (in a vat).

2. No animal can survive as just a cerebrum.

3. So, people are not animals.

But presumably the reason for thinking that an animal can’t survive as just a cerebrum is that a cerebrum makes an insufficient contribution to the animal functions. But the tail of a snake makes an even less significant contribution to the animal functions. Hence:

4. If a snake can survive as just a tail, a mammal can survive as just a cerebrum.

5. A snake can survive as just a tail.

6. So, a mammal can survive as just a cerebrum.

Objection: Only physical effects are limited to the speed of light in their propagation, and the separation of form from matter is not a physical effect, so that instantly when the head is crushed, the form leaves the snake, all at once at t.

Response: Let z be the spacetime location of the tip of the snake’s tail at t. According to the object, at z the form is no longer present. Now, given my assumption that crushing takes less time than it takes for light to travel to the snake’s tail, and that in one reference frame w is just after the crushing, there will also be a reference frame according to which z is before the crushing has even started. If at z the form is no longer present, then the form has left the tip of the tail before the crushing.

In other words, if we try to get out of the initial argument by supposing that loss of form proceeds faster than light, then we have to admit that in some reference frames, loss of form goes backwards in time. And that seems rather implausible.

Cerebrums and rattles

Animalists think humans are animals. Suppose I am an animalist and I think that I go with my cerebrum in cerebrum-transplant cases. That may seem weird. But suppose we make an equal opportunity claim here: all animals that have cerebra go with their cerebra. If your dog Rover’s cerebrum is transplanted into a robotic body, then the cerebrumless thing is not Rover. Rather, Rover inhabits a robotic body or that body comes to be a part of Rover, depending on views about prostheses. And the same is true for any animal that has a cerebrum.

It initially seems weird to say that some animals can survive reduced to a cerebrum and others cannot. But it’s not that weird when we add that the ones that can’t survive reduced to a cerebrum are animals that don’t have a cerebrum.

The person who thinks survival reduced to a cerebrum is implausible for an animal might, however, say that this is what’s odd about it. An animal reduced to cerebrum lacks internal life support organs (heart, lungs, etc.) It is odd to think that some animals can survive without internal life support and others cannot.

But compare this: Some animals can partly exist in spatial locations where they have no living cells, and others cannot. The outer parts of my hairs are parts of me, but there are no living cells there. If my hair is in a room, then I am partly in that room, even if no living cells of mine are in the room. But on the other hand, there are some animals (at least the unicellular ones, but maybe also some soft invertebrates) that can only exist where they have a living cell.

One might object that the spatial case and the temporal case are different, because in the spatial case we are talking of partial presence and in the temporal case of full presence. But a four-dimensionalist will disagree. To exist at a time is to be partly present at that time. So to a four-dimensionalist the analogy is pretty strict.

Finally, compare this. Suppose Snaky a rattlesnake stretched along a line in space. Now suppose we simultaneously annihilate everything in Snaky. Now, “simultaneously” is presumably defined with respect to some reference frame F₁. Let z be a point in Snaky’s rattle located just prior (according to F₁) to Snaky’s destruction. Then Snaky is partly present at z. But with a bit of thought, we can see that there is another reference frame F₂ where the only parts of Snaky simultaneous with z are parts of the rattle: all the non-rattle parts of Snaky have already been annihilated at F₂, but the rattle has not. Then in F₂ the following is true: there is a time at which Snaky exists but nothing outside of Snaky’s rattle exists. Hence Snaky can exist as just a rattle, albeit for a very, very short period of time.

Hence even a snake can exist without its life-support organs, but only for a short period of time.

The human animal and the cerebrum

Suppose your cerebrum was removed from your skull and placed in a vat in such a way that its neural functioning continued. So then where are you: Are you in the vat, or where the cerebrum-less body with heartbeat and breathing is?

Most people say you're in the vat. So persons go with their cerebra. But the animal, it seems, stays behind—the cerebrum-less body is the same animal as before. So, persons aren't animals, goes the argument.

I think the animal goes with the cerebrum. Here's a heuristic.

• Typically, if an organism of kind K is divided into two parts A and B that retain much of their function, and the flourishing of an organism of kind K is to a significantly greater degree constituted by the functioning of A than that of B, then the organism survives as A rather than as B.

Uncontroversial case: If you divide me into a little toe and the rest of me, then since the little toe's contribution to my flourishing is quite insignificant compared to the rest, I survive as the rest. More controversially, the flourishing of the human animal is to a significantly greater degree constituted by the functioning of the cerebrum than of the cerebrum-less body, so we have reason to think the human animal goes with the cerebrum.

Another related heuristic:

• Typically, if an organism of kind K is divided into two parts A and B that retain much of their function, and B's functioning is significantly more teleologically directed to the support of A than the other way around, then the organism survives as A rather than as B.

My heart exists largely for the sake of the rest of my body, while it is false to say that the rest of my body exists largely for the sake of my heart. So if I am divided into a heart and the rest of me, as long as the rest of me continues to function (say, due to a mechanical pump circulating blood), I go with the rest of me, not the heart. But while the cerebrum does work for the survival of the rest of my body, it is much more the case that the rest of the body works for the survival of the cerebrum.

There may also be a control heuristic, but I don't know how to formulate it.