Key Arguments

• Dreyfus introduces the assumption as a 'fallback' after the psychological assumption fails: 'intelligent behavior may still be formalizable in terms of such rules and thus reproduced by machine. 1* This is the epistemological assumption.'
• He defines the two components explicitly: 'Thus, the epistemological assumption involves two claims: (a) that all nonarbitrary behavior can be formalized, and (b) that the formalism can be used to reproduce the behavior in question.'
• He distinguishes competence from performance with examples: formal rules describing the planets or the bicycle rider 'enable us to express or understand his competence, that is, what he can accomplish. It is, however, in no way an explanation of his performance.'
• He argues that, unlike physics, there 'cannot be a theory of human performance', stating his aim 'to show that a theory of competence cannot be a theory of performance: that unlike the technological application of the laws of physics to produce physical phenomena, a timeless, contextless theory of competence cannot be used to reproduce the moment-to- moment involved behavior required for human performance; that indeed there cannot be a theory of human performance.'
• He claims that, if his argument succeeds, the assumption flips from a support for AI into an argument against it: 'If this argument is convincing, the epistemological assumption, in the form in which it seems to support AI, turns out to be untenable, and, correctly understood, argues against the possibility of AI, rather than guaranteeing its success.'

Source Quotes

The computer model turns out not to be helpful in explaining what people actually do when they think and perceive, and, conversely, the fact that people do think and perceive can provide no grounds for optimism for those trying to reproduce human performance with digital computers. But this still leaves open another ground for optimism: although human performance might not be explainable by supposing that people are actually following heuristic rules in a sequence of unconscious operations, intelligent behavior may still be formalizable in terms of such rules and thus reproduced by machine. 1* This is the epistemological assumption. Consider the planets.

There is thus a subtle but important difference between the psychological and the epistemological assumptions. Both assume the Platonic notion of understanding as formalization, but those who make the psychological assumption (those in CS) suppose that the rules used in the formalization of behavior are the very same rules which produce the behavior, While those who make the epistemological assumption (those in AI) only affirm that all nonarbitrary behavior can be formalized according to some rules, and that these rules, whatever they are, can then be used by a computer to reproduce the behavior. The epistemological assumption is weaker and thus less vulnerable than the psychological assumption.

Those who fall back on the epistemological assumption have realized that their formalism, as a theory of competence, need not be a theory of human performance, but they have not freed themselves sufficiently from Plato to see that a theory of competence may not be adequate as a theory of machine performance either. Thus, the epistemological assumption involves two claims: (a) that all nonarbitrary behavior can be formalized, and (b) that the formalism can be used to reproduce the behavior in question. In this chapter we shall criticize claim (a) by showing that it is an unjustified generalization from physical science, and claim (b) by trying to show that a theory of competence cannot be a theory of performance: that unlike the technological application of the laws of physics to produce physical phenomena, a timeless, contextless theory of competence cannot be used to reproduce the moment-to- moment involved behavior required for human performance; that indeed there cannot be a theory of human performance.

Thus, the epistemological assumption involves two claims: (a) that all nonarbitrary behavior can be formalized, and (b) that the formalism can be used to reproduce the behavior in question. In this chapter we shall criticize claim (a) by showing that it is an unjustified generalization from physical science, and claim (b) by trying to show that a theory of competence cannot be a theory of performance: that unlike the technological application of the laws of physics to produce physical phenomena, a timeless, contextless theory of competence cannot be used to reproduce the moment-to- moment involved behavior required for human performance; that indeed there cannot be a theory of human performance. If this argument is convincing, the epistemological assumption, in the form in which it seems to support AI, turns out to be untenable, and, correctly understood, argues against the possibility of AI, rather than guaranteeing its success.

In this chapter we shall criticize claim (a) by showing that it is an unjustified generalization from physical science, and claim (b) by trying to show that a theory of competence cannot be a theory of performance: that unlike the technological application of the laws of physics to produce physical phenomena, a timeless, contextless theory of competence cannot be used to reproduce the moment-to- moment involved behavior required for human performance; that indeed there cannot be a theory of human performance. If this argument is convincing, the epistemological assumption, in the form in which it seems to support AI, turns out to be untenable, and, correctly understood, argues against the possibility of AI, rather than guaranteeing its success. Claim (a), that all nonarbitrary behavior can be formalized, is not an axiom.

Key Concepts

• intelligent behavior may still be formalizable in terms of such rules and thus reproduced by machine. 1* This is the epistemological assumption.
• those who make the epistemological assumption (those in AI) only affirm that all nonarbitrary behavior can be formalized according to some rules, and that these rules, whatever they are, can then be used by a computer to reproduce the behavior.
• Thus, the epistemological assumption involves two claims: (a) that all nonarbitrary behavior can be formalized, and (b) that the formalism can be used to reproduce the behavior in question.
• a timeless, contextless theory of competence cannot be used to reproduce the moment-to- moment involved behavior required for human performance; that indeed there cannot be a theory of human performance.
• correctly understood, argues against the possibility of AI, rather than guaranteeing its success.

Context

Opening of 'The Epistemological Assumption' chapter, where Dreyfus formulates the weaker assumption adopted by AI after his critique of the psychological assumption and outlines his plan to criticize both its components.