Philosophy and mind
BCS 153, Spring 2018
They're made out of ...
https://www.youtube.com/watch?v=7tScAyNaRdQ
The mind-body problem
● How do the phenomena of minds (consciousness, beliefs, etc.) arise out of a physical system?
● Quick terminology:
● Qualia – subjective experience of something. E.g. the color green, taste of grapefruit
Substance dualism
● Substance dualism – there are two kinds of things: mental (souls) and physical (brains) (Famously, Descartes)
● Famously, Descartes:
● Bodies are “just” machines
● Machines can do a lot (digestion, heart, growth, perception, action)
● But not sensation, imagination, causation, etc.
● The soul interacts with the body through the pineal gland
Descartes' Dualism
More modern dualism
● The “soul” could be viewed as hypothesis for resolving the mind-body problem – what makes humans special is that we have non-physical processes supporting our cognition.
● Where does subjective experience come from? (Could a computer ever have a subjective experience?)
● Consciousness?
● Beliefs, desires, emotions?
● How do we fit physical changes with subjective continuity?
● Are you the same if I swap out all of the molecules in your body for other ones? What if I duplicate them? (Does your clone have your consciousness?)
Why most scientists and philosophers aren't substance dualists
● Interaction problem – how do physical and non-physical substances interact and why?
● (How does this work over the course of evolution?)
● Physical coupling problem – mental events really do seem to be linked to physical changes. – Clear degredation in behavior/thinking with physical changes (alzheimers, split brain, stroke, etc.)
Physical Causality: Penfield
● Local stimulation of epilepsy patient brains
https://www.youtube.com/watch?v=Rqxhdffo_0c
Alien hand syndrome
● Split brain patients: Cut the corpus callosum to try to treat severe epilepsy.
● May give rise to splitting of intentions – One hand buttons a dress, the other unbuttons – One hand reaches in a drawer, the other slams it shut.
https://www.youtube.com/watch?v=ZMLzP1VCANo
Another kind of dualism
● Property dualism – there is only one kind of thing (physical), but there are two kinds of properties (physical and mental). They are not the same.
The knowledge argument against physicalism (Jackson 1982)
Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specialises in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like "red," "blue," and so on. She discovers, for example, just which wave-length combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal chords and expulsion of airfrom the lungs that results in the uttering of the sentence "The sky is blue."
The knowledge argument against physicalism
Physicalism – the alternative
● Physicalism: All there is is physical
● Behaviorism – mental states are tendencies to behave certain ways.
● Identity theory – mental states are the same as physical states
● Functionalism – mental states are characterized by the relationship to other mental states.
Identity theory
● Mental events are the same as physical events.
● Imagine Penfield stimulates an area that gives you a smell percept of cinnamon.
● Identity theory say that smelling cinnamon is identical with activity in that brain area.
Critiques of identity theory
● Multiple realizability – “the same” mental states can be realized in different systems (e.g. a brain with a part replaced)
(If a Turing machine can simulate any computation, can it simulate the computation in the human brain? What if it simulated all of the particles in the brain?)
Neuroprosthetics Bensmaia & Miller (2014)
Neural prosthetics for memory (Berger et al. 2011)
Physicalism – the alternative
● Physicalism: All there is is physical
● Behaviorism – mental states are tendencies to behave certain ways.
● Identity theory – mental states are the same as physical states
● Functionalism – mental states are characterized by their functional role in the system.
Functionalism
● Functionalism – mental states can be understood through their functional role (causal connections to input, output, other mental states)
Points in favor of functionalism
● Compatible with physical accounts of the brain (and thus neuroscience, biology, psychology)
● Provides a theory of realization / implementation.
● Permits multiple realizability
● Nice characterization of many concepts:
● What does it mean for someone to be a grandmother?
● What is a mental representation of an “airport hub”?
Critiques of functionalism
● Ned Block's China Brain
Critiques of functionalism
Suppose we convert the government of China to functionalism, and we convince its officials to realize a human mind for an hour. We provide each of the billion people in China (I chose China because it has a billion inhabitants) with a specially designed two- way radio that connects them in the appropriate way to other persons and to the artificial body mentioned in the previous example. We replace each of the little men with a citizen of China plus his radio. Instead of a bulletin board we arrange to have letters displayed on a series of satellites placed so that they can be seen from anywhere in China.
The system of a billion people communicating with one another plus satellites plays the role of an external "brain" connected to the artificial body by radio. There is nothing absurd about a person being connected to his brain by radio. Perhaps the day will come when our brains will be periodically removed for cleaning and repairs. Imagine that this is done initially by treating neurons attaching the brain to the body with a chemical that allows them to stretch like rubber bands, thereby assuring that no brain-body connections are disrupted. Soon clever businessmen discover that they can attract more customers by replacing the stretched neurons with radio links so that brains can be cleaned without inconveniencing the customer by immobilizing his body.
It is not at all obvious that the China-body system is physically impossible. It could be functionally equivalent to you for a short time, say an hour.
Inverted Spectrum
● Inverted spectrum argument – Suppose I had an inverted spectrum compared to you. Your and my cognitive representations of spectra could have identical functional roles, but would give rise to different qualia. Therefore, functional role can't be the whole story.
Inverted Spectrum
Theories of mind
● Dualism:
● Substance dualism – there are two kinds of things: mental (souls) and physical (brains)
● Property dualism – there is only one kind of thing (physical), but there are two kinds of properties (physical and mental). They are not the same.
● Physicalism: All there is is physical
● Behaviorism – mental states are tendencies to behave certain ways.
● Identity theory – mental states are the same as physical states
● Functionalism – mental states are characterized by their functional role in the system.