Key Arguments

• Dreyfus presents Fodor’s starting point: 'some of the physical transactions that take place in the central nervous system when we make estimates of depth, must satisfy such descriptions as 'monitoring texture gradients', 'processing information about texture gradients', 'computing derivatives of texture gradients', etc.'
• From this, Fodor 'thus arrives at the view that "every operation of the nervous system is identical with some sequence of elementary operations."'
• Dreyfus objects that 'computing the first derivative of a texture gradient is the sort of operation very likely to be performed by some sort of analogue device,' so 'There is, therefore, no reason at all to conclude from the fact that the nervous system responds to differences in texture gradients that "every operation of the nervous system is identical with some sequence of elementary operations. . . ."'
• He finds 'not the slightest justification for the claim that "for each type of behavior in the repertoire of that organism, a putative answer to the question, How does one produce behavior of that type? takes the form of a set of specific instructions for producing the behavior by performing a set of machine operations."'
• He illustrates the fallacy with analogies: 'to say that the brain is necessarily going through a series of operations when it takes the texture gradient is as absurd as to say that the planets are necessarily solving differential equations when they stay in their orbits around the sun, or that a slide rule (an analogue computer) goes through the same steps when computing a square root as does a digital computer when using the binary system to compute the same number.'
• He extends the analogy to an ion solution reaching equilibrium: 'Does the solution, in reaching equilibrium, go through the series of discrete steps a digital computer would follow in solving the equations which describe this process?' and points out that if so 'the solution is solving in moments a problem which it would take a machine centuries to solve.'
• He concludes that 'The fact that we can describe the process of reaching equilibrium in terms of equations and then break up these equations into discrete elements in order to solve them on a computer does not show that equilibrium is actually reached in discrete steps,' and likewise 'we need not conclude from the fact that all continuous physicochemical processes involved in human "information processing" can in principle be formalized and calculated out discretely, that any discrete processes are actually taking place.'
• Dreyfus also notes a methodological slippage: Fodor’s choice of texture‑gradient estimation—'one of the least plausible cases in which one would want to argue that the brain or the mind is performing any elementary operations at all'—suggests he thinks 'there is some kind of necessary connection between taking a texture gradient, computing, and performing a sequence of operations.'

Source Quotes

It is instructive to follow his argument. Fodor begins with generally accepted facts about the central nervous system: If the story about the causal determination of depth estimates by texture gradients is true and if the central nervous system is the kind of organ most sensitive people now think it is, then some of the things the central nervous system does, some of the physical transactions that take place in the central nervous system when we make estimates of depth, must satisfy such descriptions as 'monitoring texture gradients', 'processing information about texture gradients', 'computing derivatives of texture gradients', etc. 7 He thus arrives at the view that "every operation of the nervous system is identical with some sequence of elementary operations."8 Disregarding the question-begging use of "processing information" in this account, we can still object that computing the first derivative of a texture gradient is the sort of operation very likely to be performed by some sort of analogue device. There is, therefore, no reason at all to conclude from the fact that the nervous system responds to differences in texture gradients that "every operation of the nervous system is identical with some sequence of elementary operations. . . .

Fodor begins with generally accepted facts about the central nervous system: If the story about the causal determination of depth estimates by texture gradients is true and if the central nervous system is the kind of organ most sensitive people now think it is, then some of the things the central nervous system does, some of the physical transactions that take place in the central nervous system when we make estimates of depth, must satisfy such descriptions as 'monitoring texture gradients', 'processing information about texture gradients', 'computing derivatives of texture gradients', etc. 7 He thus arrives at the view that "every operation of the nervous system is identical with some sequence of elementary operations."8 Disregarding the question-begging use of "processing information" in this account, we can still object that computing the first derivative of a texture gradient is the sort of operation very likely to be performed by some sort of analogue device. There is, therefore, no reason at all to conclude from the fact that the nervous system responds to differences in texture gradients that "every operation of the nervous system is identical with some sequence of elementary operations. . . . " There is, indeed, not the slightest justification for the claim that "for each type of behavior in the repertoire of that organism, a putative answer to the question, How does one produce behavior of that type? takes the form of a set of specific instructions for producing the behavior by performing a set of machine operations.''9 The argument gains its plausibility from the fact that if a psychologist were to take the first derivative of a texture gradient, he would compute it using a formalism (differential calculus) which can be manipulated in a series of discrete operations on a digital computer.

There is, therefore, no reason at all to conclude from the fact that the nervous system responds to differences in texture gradients that "every operation of the nervous system is identical with some sequence of elementary operations. . . . " There is, indeed, not the slightest justification for the claim that "for each type of behavior in the repertoire of that organism, a putative answer to the question, How does one produce behavior of that type? takes the form of a set of specific instructions for producing the behavior by performing a set of machine operations.''9 The argument gains its plausibility from the fact that if a psychologist were to take the first derivative of a texture gradient, he would compute it using a formalism (differential calculus) which can be manipulated in a series of discrete operations on a digital computer. But to say that the brain is necessarily going through a series of operations when it takes the texture gradient is as absurd as to say that the planets are necessarily solving differential equations when they stay in their orbits around the sun, or that a slide rule (an analogue computer) goes through the same steps when computing a square root as does a digital computer when using the binary system to compute the same number.

" There is, indeed, not the slightest justification for the claim that "for each type of behavior in the repertoire of that organism, a putative answer to the question, How does one produce behavior of that type? takes the form of a set of specific instructions for producing the behavior by performing a set of machine operations.''9 The argument gains its plausibility from the fact that if a psychologist were to take the first derivative of a texture gradient, he would compute it using a formalism (differential calculus) which can be manipulated in a series of discrete operations on a digital computer. But to say that the brain is necessarily going through a series of operations when it takes the texture gradient is as absurd as to say that the planets are necessarily solving differential equations when they stay in their orbits around the sun, or that a slide rule (an analogue computer) goes through the same steps when computing a square root as does a digital computer when using the binary system to compute the same number. Consider an ion solution which might be capable of taking a texture gradient or of simulating some other perceptual process by reaching equilibrium.

Key Concepts

• must satisfy such descriptions as 'monitoring texture gradients', 'processing information about texture gradients', 'computing derivatives of texture gradients', etc.
• He thus arrives at the view that "every operation of the nervous system is identical with some sequence of elementary operations."
• There is, therefore, no reason at all to conclude from the fact that the nervous system responds to differences in texture gradients that "every operation of the nervous system is identical with some sequence of elementary operations. . . . "
• " There is, indeed, not the slightest justification for the claim that "for each type of behavior in the repertoire of that organism, a putative answer to the question, How does one produce behavior of that type?
• to say that the brain is necessarily going through a series of operations when it takes the texture gradient is as absurd as to say that the planets are necessarily solving differential equations when they stay in their orbits around the sun, or that a slide rule (an analogue computer) goes through the same steps when computing a square root as does a digital computer when using the binary system to compute the same number.

Context

Central critical passage in the Psychological Assumption section where Dreyfus dissects Fodor’s argument and uses physical analogies (planets, slide rules, ion solutions) to show that mathematical description does not entail discrete computational implementation.