We have spoken of folk psychology. Eliminativism proposes that folk psychology is a weak theory of human behaviour, destined to be replaced.
Folk psychology is the name some theorists have given to our ordinary way of talking about human actions springing from what they want and what they believe will get them what they want. Why did I bring my keys? Because I want to get back in the house, and think the keys will be necessary for that.
Folk psychology is deeply embedded in human life. It is at the foundation of all our social and legal arrangements, and also in most of what we say and think about ourselves and others. So the claim that it is simply a mistaken theory is a dramatic and far reaching one. Entertaining it is an exercise in thinking the unthinkable. -And of course invaluable for a philosophical person for that reason.
Eliminativists believe it will be replaced by the theory of the workings of the brain and the central nervous system which is emerging from neuroscience. We will come to explain and predict what we do - better, our behaviour - not in terms of beliefs and desires, but in terms of neurones, synapses, ganglia, neurotransmitters, etc.
In his paper in the Reader, Paul Churchland spends the first part trying to show that folk psychology is indeed a theory. And that of course is the first critical step. It was a novel and surprising suggestion that our ordinary way of thinking about action was a theory. You may find it surprising that the suggestion has got established and gained ground. Churchland's article sprouts equations in the course of his discussion of this point. It is skippable if necessary. Pick it up again on page 210, the beginning of Section II.
But he is only saying that FP yields law like statements like this:
For all x and for all p
if x fears that p then x desires that not p
or
For all x and for all p
if x hopes that p and x discovers that p then x is pleased that p
He then argues that when you think about it is a poor theory. It fails in the following areas for example:
The nature and dynamics of mental illness
the faculty of creative imagination
the ground of intelligence differences between individuals
the nature and psychological significance of sleep, which ordinarily occupies one third of a person's life
catching
hitting targets when we throw
the construction of 3D visual images from 2D retinal patterns
perceptual illusions
memory
learning
BUZZ Which of these does have light shed on it by FP?
Summary: 'On these and other mental phenomena, Folk Psychology sheds negligible light.'. (Churchland, in Lycan, p.210)
Plenty of theories that seem common-sense at one time are abandoned later.
Theories once sponsored by common sense:
space has a preferred direction in which things fall
weight is an intrinsic feature of a body
a force-free moving object will promptly return to rest
the sphere of the heavens turns daily
To suggest that FP will be abandoned is not absurd.
Two fates for FP:
Reduction of one theory to another is said to take place when there are equivalent concepts in either theory - those in one correspond to those in another.
This is the kind of relationship envisaged by the identity hypothesis. There is an alleged equivalence between lightening and electrical discharge, clouds and moisture droplets, consciousness and brain activity.
Coloric theory
There was a theory of heat which postulated that it was a fluid - a special fluid, one a fluid which couldn't be felt, and didn't weigh anything, but occupied space. So the expansion of bodies when they became hot was accounted for, and the fact that heating a body didn't in itself increase their weight.
What replaced this theory was the hypothesis that heat was a form of energy.
Paul Churchland in the Reader article says that Folk Psychology could be heading for either fate.
Later he favours the latter. It is set to be eliminated by neuroscience.
This is eliminative materialism.
"Folk psychology suffers explanatory failures on an epic scale...it has been stagnant for at least 25 centuries, and ... its categories appear ... incommensurable with ... the categories of the background physical science whose long-term claim to explain human behaviour seems undeniable."
Churchland, in Lycan, p.212.