Canada and California, born 1942 and 1943
Paul and Patricia Churchland
Our everyday talk of beliefs, desires and feelings is a theory, and like other folk theories it may turn out to be false. If so, the right response is not to defend it but to replace it with what neuroscience finds.
The view
The Churchlands are married philosophers who spent most of their careers at the University of California, San Diego. Patricia Churchland's Neurophilosophy (1986) argued that questions about the mind cannot be settled from the armchair, and that philosophers must learn neuroscience. The word in her title became the name of a field. Paul Churchland's "Eliminative Materialism and the Propositional Attitudes" (1981) made the more startling claim. Folk psychology, our everyday framework of beliefs and desires, is an empirical theory. It may be as mistaken as the folk physics of impetus or the folk chemistry of phlogiston, and if it is, a mature neuroscience will eliminate it rather than explain it.
Paul Churchland pointed to how little folk psychology has advanced in two thousand years, and how much it fails to explain: sleep, mental illness, learning, memory, the variety of intelligence. A theory with that record, he argued, should not be immune from replacement.
The argument
Folk psychology is a theory, and quite possibly a radically false one. After Paul Churchland, "Eliminative Materialism and the Propositional Attitudes" (1981)
The positive picture is of the brain as a vast network computing with patterns of activity across populations of neurons. A state of the brain is a point in a "state space" with one dimension for each neuron or group of neurons. Paul Churchland's best-known example is colour. Colour vision begins with three kinds of cone, sensitive to short, medium and long wavelengths. Any colour you see corresponds to a point in the three-dimensional space of their activity, later recoded into opponent channels. Similar colours are nearby points; complementary colours are opposite. On this picture the felt relations between colours, that orange is between red and yellow and that no colour is reddish green, are geometry.
The figure simplifies a great deal: real cones overlap in what they detect, and the brain's coding is far richer. But the moral holds. If the qualities of experience are positions in a space of neural activity, there is nothing left over for the word "qualia" to name. Paul Churchland went further, predicting that people who learned the neuroscience well might come to perceive and describe their own experiences in its terms, as an astronomer sees a planet where others see a bright star.
Where they meet Dennett
The Churchlands and Dennett were long-standing allies against dualism, against qualia and against the idea that introspection gives infallible access to the mind. All three wanted philosophy to answer to science. All three were attacked as "denying consciousness", and all three replied that what they denied was a particular theory of consciousness.
Where they part
The sharpest difference is over folk psychology. Dennett defended it. Beliefs and desires, he said, are real patterns, visible from the intentional stance, and they would survive any advance in neuroscience in the way centres of gravity survive advances in physics. The Churchlands took them to be posits of a theory that might be false. Dennett thought eliminativism threw out something that works. The Churchlands thought his "real patterns" were a halfway house.
There is a difference of approach too. The Churchlands build upward from neurons. Dennett worked downward from the functional level, from what a system has to be able to do, and treated neural detail as how the job gets done.
| The Churchlands | Dennett | |
|---|---|---|
| What is the mind? | The activity of neural networks, best described by neuroscience. | What the brain does: a pattern of functions. |
| Is phenomenal consciousness real? | Experience is real; qualia, as a separate category, are not. | No, not as philosophers define it. It is an illusion produced by the brain. |
| Could a machine have a mind? | Yes, if it computes as brains do. | Yes, in principle, if it does what we do. |
| Is there a hard problem? | No. It reflects ignorance, not a deep gap. | No. There is the Hard Question: and then what happens? |
Further reading
- Patricia Smith Churchland, Neurophilosophy: Toward a Unified Science of the Mind-Brain (MIT Press, 1986).
- Paul M. Churchland, The Engine of Reason, the Seat of the Soul (MIT Press, 1995): neural networks and state spaces for general readers.
- Patricia S. Churchland, Touching a Nerve: The Self as Brain (Norton, 2013).
- Eliminative materialism, Stanford Encyclopedia of Philosophy.