This article will examine two arguments. One argument is for Animalism and one is against.

Animalism:Animalism, according to Olson, is the belief that all people are numerically identical to some animal. For each person there is a unique human organism and that organism is you. (Also, this animalism doesn’t say you are essentially an animal).

Brain-Transplant Argument

            Imagine a scenario where the cerebrum in your head is transplanted to another body. It seems plausible that you would perhaps go along with your cerebrum and now be in that other body. The being that receives your cerebrum will alone be mentally continuous with you (in any relevant sense of mental continuity) so you will not stay behind with an empty head but instead go along with your cerebrum. It seems that there is a human animal now lying behind with an empty head and another human animal with which you identify.  With the story above in mind the argument would look like this:

  1. I can be separated from my human animal.
  2. No human animal can be separated from itself.
  3. Thus, by Leibniz’s law I am not a human animal.

The argument is deductively valid so to reject the conclusion one must reject one of the premises. It is my belief that Olson would probably reject premise 1. Premise 1 only holds true by the principle of mental continuity which I believe Olson would reject, even though it is not explicitly stated by Olson that this is the premise he would reject.

The Thinking Animal Argument

            This argument is based on a few acute observations: we are intimately related to some human animal, it is located where you are located (for example sitting in the same chair you are sitting in), and it seems reasonable to believe that this animal can think. From these observations we receive the following:

  1. There exists an X such that X is a human animal and X is located where you are.
  2. For all X if X is located where you are and X is a human animal the X is thinking.
  3. For all X if X is located where you are and X is thinking then X is numerically identical to you.
  4. Thus, there exists and X such that X is a human animal and X is numerically identical to you.

This argument is likewise deductively valid. So again to reject the conclusion we must reject one the premises. Part of Olson’s argument is to do exactly that. Olson walks through what would happen if you were to reject any of the three premises.

Alternative one is to reject premise A. If you reject that there is a human animal located exactly where you are at this moment then you are rejecting the existence of all human animals. If you reject that fact that human animals exist it may be hard to believe in any organism’s existence. So Olson would believe that for most of us this alternative may not seem attractive.

Alternative two is to reject premise B. If you reject premise 2 then you are accepting that human animals cannot think. It is akin to saying that there is a human animal located where you are but it isn’t thinking. This, once again, would call into question the mental properties of all organisms. Rejecting this premise may lead you to believe that no material thing can think which would be difficult to prove. Thus, some of us may not want to conclude that organisms and material things cannot think.

Alternative three is to reject premise C. If you reject this premise then you are not alone. There would be a human animal thinking all of your thoughts located exactly where you are. This is the least attractive route. I believe the creepiness alone would lead us to reject this but there are other issues as well. Of the many problems we can say that the metaphysical distinction would be almost useless to make. It wouldn’t be practical in any given situation. It would also seem impossible to understand which one you are. Are you the animal or the mind thinking all the same thoughts as the animal? Would you ever know?

Because of the alternatives above we are led to believe that the thinking-animal argument is also sound. It seems that rejecting any of the premises would result in some strange and perhaps absurd results. But, we shall still evaluate both the thinking-animal argument and the brain-transplant argument by trying to deny a premise boldly.


First, let us evaluate the brain-transplant argument. It seems at first obvious that premise 2 is indisputable (no human animal can be separated from itself) since no object can be separated from itself (essentially).  So, premise 1 seems like the only reasonable premise to refuse. Now this has interesting results either way. Let’s assume you cannot be separated from your body, that is to say, you wouldn’t go along with your cerebrum. This is plausible and we would all accept this to be a different person. Let’s say you do go along with the cerebrum (in a mental continuous sense) but you reject the fact that you are the same person. This only seems plausible if you consider a case where you receive a significantly different body. If you were to receive a body that was lacking in abilities that the other body had you might be tempted to say that by Leibniz’s law you are a different person since there is something true of you now that was false of you previously. But, perhaps it is as C.S. Lewis says “You are a soul, you have a body,” and your mind (cerebrum) can just “possess” different bodies that aren’t essentially you so Leibniz’s law would not hold. To reject this possession way of thinking one must reject mental continuity. I do not have an opinion on mental continuity but mental continuity seems more plausible to me so I am tempted to say this argument is sound. Verily, both alternatives seem plausible.

When evaluating Olson’s thinking animal argument we are left with a much more difficult task. Olson does you the favor of considering all your alternatives for you which seems to narrow things down quickly but, also makes you feel ridiculous for rejecting any of the premises. Personally, I think the only premise one can reject while remaining rational and consistent would be premise B. As we discussed, Olson asserts that this leads you to the belief that human animals cannot think. Now, this might sound ridiculous to some but if you are a dualist and consider the mind separate from the human animal then perhaps this premise isn’t so hard to negate. Referring to the C.S. Lewis quote above, some dualist would say that it is obvious that human animals don’t think, souls think.  Since, as I mentioned earlier, Olson’s animalism doesn’t commit you to being essentially an animal. So, we can say that we are essentially a mind, a ghost in the machine, a soul, what have you, and then conclude there is a thinking thing and an animal located where we are located and we are that animal, (not essentially the animal though), yet it is not the case that the animals is thinking. But, we are still the thinking animal.


I am undecided on the matter. But I do believe it is possible for souls to exist so I would lean toward that counterargument against the thinking-animal argument.

Citation: In R. Martin and J. Barresi, eds., Personal Identity, Blackwell 2003: 318-34.

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