> “We” are our brain.

Maybe not -

> Mereology is the logic of part/whole relations. The neuroscientists’ mistake of ascribing to the constituent parts of an animal attributes that logically apply only to the whole animal we shall call ‘the mereological fallacy’ in neuroscience.

> The principle that psychological predicates which apply only to human beings (or other animals) as wholes cannot intelligibly be applied to their parts, such as the brain, we shall call ‘the mereological principle’ in neuroscience.

> Human beings, but not their brains, can be said to be thoughtful or to be thoughtless; animals, but not their brains, let alone the hemispheres of their brains, can be said to see, hear, smell and taste things; people, but not their brains, can be said to make decisions or to be indecisive.

So the basic idea of the mereological fallacy (which is what the author may be committing) is claiming parts are responsible for something only the whole they are a part of can be responsible for. In neuroscience, the brain is the particular part that gets ascribed characteristics only the whole body or person can be responsible for.

I think it's easiest to deal with from the first person, since figuring out whether other people are doing things involves a variety of concerns about inferring mental activity from observed bodily behavior - though the issue is still pertinent there.

Let's just jump into some issues that just the basic first personal claim that "I think my brain is thinking" gives rise to. These are just questions to ask yourself for the sake of figuring out how to make sense of a person, a brain, and their status as either part or whole and how they can relate in a way that makes sense.

• Is my brain equivalent to my thinking, my activity in general, myself? How could it even still be just one part of a person's body if it's a whole person? Is it both a part and a whole, somehow? In what respects, such that this wouldn't be a contradiction?

• If I just were a brain, would I be part of a body that isn't my own? What of the other body parts, are they part of me or are they just sort of tools for me as a brain? How would sensation even work if that's all they are? My eyes and my brain are both important for a whole person to see colors on a theory that considers them parts, but if the brain is the whole person how does the affectation of the eye result in a brain's experience of color?

• What happens as a brain changes? If a brain is a body part of a whole person, that person can stay the same as experiencing subject as their brain develops, changes, etc. The person as a whole accounts for the unity of the body and the experiences resulting from its changes all being a process of a single subject. But if I am my brain, wouldn't I just cease to be when my brain changes, and some other brain-person would pop into being upon the instantiation of the new brain structure?

• What determines the limit of a body or body part? Why do we decide the brain material stops here, the eye material stops here, the whole person's body stops here, etc.? Why is it not just an arbitrarily selected aggregate of atomistic pieces of stuff any way you slice it?

Minimally, we can say the mereological fallacy is a criticism of a way of treating these kinds of questions that some philosophers believe does not make sense.