aIn his We are our brain the Dutch brain researcher Dick Swaab makes us think not only about the free will (see my blog two weeks ago), but also about our personal identity. His discussion of the subject is especially relevant for the question whether this identity is determined by psychological factors, by bodily factors or by both. One of the weak points of the pure psychological approach is that it denies that our personal identity is at least partially dependent on our physical constitution. Its adherents reject not only the importance of our bodily characteristics for our identity but they ignore also the way psychological characteristics are fixed in our body. They do accept that our psychological characteristics are physically fixed in our body in some way, indeed, for what sense would a brain swap have, if it weren’t? But they do not see that many psychological characteristics are not fixed to our body like a painting on a canvass (which makes that we can replace the canvass and keep the painting, albeit with much effort), but that they are inextricably tied to our material structure and are dependent on the individual features of our brain and in the end on the structure of our DNA.The foregoing is not a pure philosophical problem. It may get a practical meaning as soon as it will become possible to transplant brain tissue from a foetus for repairing defects in another brain, as Swaab explains. For since “many of our characteristics, including our character, are determined in the structure of our brain during our foetal development … which characteristics could you get then from your donor?”, Swaab asks. These characteristics are dependent on what part of the foetus brain is used for the transplantation and where it will be placed in the donor’s brain. When this technique can be realized, especially in the higher brain structure, “it is to be wondered to what extent a new person is being composed, and how much transplanted tissue makes that the receiver should actually use the name of the donor as his second family name”. The issue of personal identity will become even more interesting, Swaab adds, when we are going to use tissues from other creatures for our brain transplantations. Until now these operations were hardly successful, “[b]ut if such xenotransplantations should ever become effective, would these transplants provide man then [for instance] with a bit of the friendliness and intelligence of the pigs?” If that is so, maybe it would not be a bad idea to improve our identity as a person in this way. (See Swaab, Wij zijn ons brein, pp. 170-1, also for the quotations).