Amazon Book Description
- Could a single human being ever have multiple conscious minds? Some human beings do. The corpus callosum is a large pathway connecting the two hemispheres of the brain. In the second half of the twentieth century a number of people had this pathway cut through as a treatment for epilepsy. They became colloquially known as split-brain subjects. After the two hemispheres of the brain are cortically separated in this way, they begin to operate unusually independently of each other in the realm of thought, action, and conscious experience, almost as if each hemisphere now had a mind of its own.
- Philosophical discussion of the split-brain cases has overwhelmingly focused on questions of psychological identity in split-brain subjects, questions like: how many subjects of experience is a split-brain subject? How many intentional agents? How many persons? On the one hand, under experimental conditions, split-brain subjects often act in ways difficult to understand except in terms of each of them having two distinct streams or centers of consciousness. Split-brain subjects thus evoke the duality intuition: that a single split-brain human being is somehow composed of two thinking, experiencing, and acting things. On the other hand, a split-brain subject nonetheless seems like one of us, at the end of the day, rather than like two people sharing one body. In other words, split-brain subjects also evoke the unity intuition: that a split-brain subject is one person.
- Elizabeth Schechter argues that there are in fact two minds, subjects of experience, and intentional agents inside each split-brain human being: right and left. On the other hand, each split-brain subject is nonetheless one of us. The key to reconciling these two claims is to understand the ways in which each of us is transformed by self-consciousness1.
- Elizabeth Schechter is an assistant professor of philosophy and a member of the Philosophy-Neuroscience-Psychology Program at Washington University in St. Louis.
Contents of Book
- The Unity Puzzle – 1
- Subjects of Experience and Subjective Perspectives – 23
- Dual Intentional Agency – 50
- How Many Minds? – 80
- Objection from Sub-Cortical Structures – 107
- Bodies and Being One – 139
- Self and Other in the Split-Brain Subject – 156
- The Self-Consciousness2 Condition of Personhood – 181
- Duality Myths – 211
Contents of Chapter 1: The Unity Puzzle
- The Dual Brain – 1
- The Split-Brain Surgeries – 4
→ 2.1. The first split-brain surgeries – 5
→ 2.2. The discovery of the split-brain phenomenon – 5
→ 2.3. The first split-brain experiments – 8
→ 2.4. Working with split-brain human beings – 11
- The Unity Debates – 15
- Outline of Book3 – 18
- On Paths Not Taken – 19
Outline of Book
- Chapter 2 “Subjects of Experience and Subjective Perspectives” presents the case for thinking that a split-brain subject has two subjective perspectives. This 2-perspectives claim is entailed by three others:
Chapter 2 also rejects challenges to the interhemispheric disunity claim, and explains why the truth of the 2-perspectives claim suggests that the two hemispheres are associated with distinct subjects of experience, whom I call R and L. Because of the close connections between consciousness and agency, the truth of this latter 2-subjects claim ultimately depends upon it being the case that R and L are distinct intentional agents.
- that there are elements of experience associated with both the right hemisphere and the left hemisphere,
- that these elements are unified intrahemispherically, and
- that they are disunified interhemispherically.
- Chapter 3 “Dual Intentional Agency” defends this 2-agents claim, and explains why it is consistent with what we know about split-brain subjects’ behavior even outside of experimental conditions, in their daily lives.
- Chapter 4 “How Many Minds?” generalizes the defense of the 2-subjects and 2-agents claims, explaining who R and L are, and how there could be two distinct psychological beings, two thinkers, co-embodied as one human being. What is puzzling about the 2-thinkers claim is that R’s mental states interact with L’s richly and perpetually. The argument for the 2-thinkers claim therefore appeals to different kinds of psychic interaction and independence and especially to what I call the distinction between direct versus indirect mental state interaction. What evokes the various duality intuitions are cases in which R’s mental states seem able to interact with L’s only indirectly. Chapter 4 explains why this distinction matters to the individuation of thinkers.
- Chapter 5 “Objection from Sub-Cortical Structures” concerns the major objection to the 2-thinkers claim, the objection from sub-cortical structures, according to which split-brain psychology is ultimately not substantially divided by split-brain surgery. Chapter 5 argues that remaining direct interhemispheric interaction is neither substantial nor the primary source of what unity and normalcy we see in split-brain subjects’ behavior. The best account of split-brain psychology is thus still one according to which a split-brain subject is two distinct psychological beings, albeit beings that are neither physically nor psychologically discrete. Several philosophers have presented arguments to the effect that if the duality claims are true of split-brain subjects, then they must be true of non-split subjects also, since we are all unitary human beings with two cerebral hemispheres.
- Chapter 6 “Bodies and Being One” responds to and rejects these arguments, and then presents the kind of psychological commonality between non-split and split-brain subjects that is secured by the unity of the body.
- Chapter 7 “Self and Other in the Split-Brain Subject” turns to self-consciousness4 in split-brain subjects, arguing that R and L are not just distinct thinkers but distinct thinkers of I-thoughts in particular. In this sense, self-consciousness5 is dual in split-brain subjects. On the other hand, split-brain self-consciousness6 operates in such a way as to make R and L very different from other pairs of self-conscious thinkers.
- This will become the basis of Chapter 8’s argument – “The Self-Consciousness7 Condition of Personhood” – that R and L are not distinct persons but are instead mere parts of one person.
- Chapter 9 “Duality Myths” turns again to the relationship between the split-brain and the non-split case, and in particular to the question of why the split-brain cases garnered so much interest and attention even from non-academic quarters. There I offer a different explanation from the one standardly offered — including in Section 3 of this chapter.
- TOC and Chapter 1 of the book, ...
- For the text, see Link.
- Uncorrected proof - 9th April 2018.
- Book published by OUP Oxford (14 June 2018): 320pp; too expensive at £50.
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2019
- Mauve: Text by correspondent(s) or other author(s); © the author(s)