In The Concept of Mind, Gilbert Ryle admits to having been taken in by the body-mind dualism which permeates Western philosophy, and claims that the idea of Mind as an independent entity, inhabiting and governing the body, should be rejected as a redundant piece of literalism carried over from the era before the biological sciences became established. The proper function of Mind-body language, he suggests, is to describe how higher organisms such as humans demonstrate resourcefulness, strategy, the ability to abstract and hypothesize and so on from the evidences of their behavior.

He attacks the idea of 17th and 18th century thinkers (such as Descartes and La Mettrie) that nature is a complex machine, and that human nature is a smaller machine with a “ghost” in it to account for intelligence, spontaneity and other such human qualities. While mental vocabulary plays an important role in describing and explaining human behavior, neither are humans analogous to machines nor do philosophers need a “hidden” principle to explain their super-mechanical capacities.

Ryle asserted that the workings of the mind are not distinct from the actions of the body. They are one and the same. Mental vocabulary is, he insists, merely a different manner of describing action. He also claimed that the nature of a person’s motives are defined by that person’s dispositions to act in certain situations. There are no overt feelings, pains, or twinges of vanity. There is instead a set of actions and feelings that are subsumed under a general behavior-trend or propensity to act, which we term “vanity.”

Novelists, historians and journalists, Ryle points out, have no trouble in ascribing motives, moral values and individuality to people’s actions. It is only when philosophers try to attribute these qualities to a separate realm of mind or soul that the problem arises. Ryle also created the classic argument against cognitivist theories of explanation, Ryle’s Regress.

This argument concludes that such theories are essentially meaningless as they do not explain what they purport to explain. Ryle was concerned with what he called the intellectualist legend (also known as the “dogma of the ghost in the machine,” the “Two-Lives Legend,” the “Two-Worlds Story,” or the “Double-Life Legend”) which requires intelligent acts to be the product of the conscious application of mental rules.

A fine summation of the position which Ryle is combating is the famous statement by Emerson that, “The ancestor of every action is a thought.” In sharp contrast to such assertions, which rule out any other possible parentage to actions by the use of the word “every,” Ryle argued that the intellectualist legend results in an infinite regress of thought:

According to the legend, whenever an agent does anything intelligently, his act is preceded and steered by another internal act of considering a regulative proposition appropriate to his practical problem. […] Must we then say that for the hero’s reflections how to act to be intelligent he must first reflect how best to reflect how to act? The endlessness of this implied regress shows that the application of the criterion of appropriateness does not entail the occurrence of a process of considering this criterion.
The crucial objection to the intellectualist legend is this. The consideration of propositions is itself an operation the execution of which can be more or less intelligent, less or more stupid. But if, for any operation to be intelligently executed, a prior theoretical operation had first to be performed and performed intelligently, it would be a logical impossibility for anyone ever to break into the circle.

Variants of Ryle’s regress are commonly aimed at cognitivist theories. For instance, in order to explain the behavior of rats, Edward Tolman suggested that the rats were constructing a “cognitive map” that helped them locate reinforcers, and he used intentional terms (e.g., expectancies, purposes, meanings) to describe their behavior. This led to a famous attack on Tolman’s work by Guthrie who pointed out that if one was implying that every action must be preceded by a cognitive ‘action’ (a ‘thought’ or ‘schema’ or ‘script’ or whatever), then what ’causes’ this act? Clearly it must be preceded by another cognitive action, which must in turn be preceded by another and so on, in an infinite regress.

As a further example, we may take note of the following statement from The Concept of Mind:

“The main object of this chapter is to show that there are many activities which directly display qualities of mind, yet are neither themselves intellectual operations nor yet effects of intellectual operations. Intelligent practice is not a step-child of theory. On the contrary theorizing is one practice amongst others and is itself intelligently or stupidly conducted.”

In light of Ryle’s critique, we may translate the statement by Emerson (still very much in common currency) into, “The ancestor of every action is an action.” (This is so, since Ryle notes that, “theorizing is one practice amongst others.”) With some verbal substitution, we may translate the Emerson quote further into, “The ancestor of every behavior is a behavior,” (the latter of which, according to the intellectualist legend, would require yet another behavior to preface it as its ancestor, and we have entered an infinite regress).

Ryle’s regress is a critique of cognitivism arising from the Behaviorist tradition. Near the end of The Concept of Mind, Ryle states

The Behaviorists’ methodological program has been of revolutionary importance to the program of psychology. But more, it has been one of the main sources of the philosophical suspicion that the two-worlds story is a myth.

Ryle’s brand of logical behaviorism is not to be confused with the radical behaviorism of B.F. Skinner, or the methodological behaviorism of John B. Watson. Alex Byrne noted that “Ryle was indeed, as he reportedly said, ‘only one arm and one leg a behaviorist’.”

Cognitive scientists have Ryle’s regress as a potential problem with their theories. A desideratum for those is a principled account of how the (potentially) infinite regress that emerges can be stopped.