Julie is getting a Wada procedure, the alternate suppression of each hemisphere of her brain. In effect it turns her into two different people. Where does the self go?
I was working with psychotic patients at the time, and I particularly enjoyed my conversations with one of my patients, Ron, who would discourse at length on politics, art and science, and who gave cogent accounts of his brilliant, but curtailed, academic career. And then he would flip. He entered a parallel, paranoid universe; an alternative history in which he had served as Princess Anne’s bodyguard, but was now being persecuted by agents of the royal family. Why? Because he had betrayed a terrible secret: the princess had given birth to Siamese twin daughters and hidden them away. One of the brightest people I ever met, Ron was also the most resolutely insane. He refused medication, preferring to meet his madness head on. (…)
Then there are the extremely rare cases of “dicephalic parapagus” (one trunk, two heads) and “diprosopic parapagus” (one trunk, one head, two faces).
Is it possible in such cases to determine the number of persons present? Philosophers delineate various conditions of personhood, among them: humanity (membership of the human race), identity (psychological continuity over time), and individuation (factors distinguishing one person from another). Conjoined twins clearly meet the first two conditions but create confusion over the third. If bodily functions and/or brain activity are to some extent shared then, arguably, the individuation of conjoined twins is only partial. There is neither one person nor two.
