We all know that it's in the head and, within the head, in the brain. Beyond that, though, things are a bit murky, as (modern neuroscience not withstanding) we don't know just what happens where in the brain. But it wasn't always obvious that the mind is in the head. Victor Mair has a fascinating post over at Language Log dealing with Chinese conceptions of the mind. He starts by quoting from
The Atlantic:
Rather, I would like to concentrate on a problem raised in this key sentence from the section of the article titled "Decisions are made from the heart":
Americans tend to believe that humans are rational creatures who make decisions logically, using our brains. But in Chinese, the word for "mind" and "heart" are the same.
What can we say about this identification of "heart" and "mind" (xīn 心)? In what way is true? In what way is it misleading?
Because of uncertainty over how to translate xīn 心, whether as "heart" or "mind", some scholars have taken to rendering it as "heart-mind" or "heart / mind", while others feel that it should be translated as "heart" or as "mind" depending upon the context. It becomes problematic when one insists on translating it either as "heart" or as "mind" in all cases.
He asked a number of experts about this and lists their replies, which are fascinating. Mair concludes:
So, we've covered a lot of ground in this inquiry, from the heart to the mind to thought and the mind-body problem. But where in all this is the self located? When it comes to the self, there was little hesitation among premodern Chinese in locating it in the nose. Indeed, the early forms of the graph for zì 自 ("self") depicted a nose.
My wife (and many other Chinese friends and acquaintances) actually emphatically pointed to her nose (placed the end of her index finger on the tip of her nose) when she would say, "Wǒ zìjǐ 我自己" ("I myself").
For traditional Chinese, the mind may have been in the heart, but the self was in the nose.
Here's a comment I added:
On the nose and the self, I believe that the rhinencephalon ("nose" brain) is the phylogenetically oldest part of telencephalon, the embryonic structure that matures into the cerebrum, consisting of the cortices. It's worth noting that the sense of smell looms larger in the sensorium of most animals than it does in ours and that it is through smell that animals identify individual conspecifics. That, presumbably, is why our canine friends can be used to track us individually when we escape from prison. I've read of experiments in which mothers can identify by smell diapers than have been on their infants, though I have no citations to offer. So I'd say that locating the self in the nose is a pretty shrewd move.
More generally, the mental body and its organs do not, of course, have external physical manifestations. We can't see and touch them. So figuring out just what and where they are is no trivial matter, which is why modern govenments are investing billions of dollars in neuroscience.
I echo J. W. Brewer's thoughts on the ancient Greeks. Just what Plato in fact knew of his nervous system isn’t quite clear. But he certainly didn’t have anything approaching a contemporary understanding. We know that he believed humans to be animated by three souls, one located in the head and concerned with reason, another in the breast (“midway between the midriff and the neck”) and concerned with the passions, while the third was located in and about the liver (“between the midriff and the boundary of the navel”) and concerned itself with physical appetite (Timeus 69d-71b). We now know that control of all of these functions is located in the brain, which is located in the head.