Friedrich August von Hayek, The Sensory Order after 25 Years

Hayek’s conference essay, delivered in 1977, first published in 1982, and republished in the supplied 2017 edition, reconsiders the origins, explanatory ambitions, and philosophical consequences of The Sensory Order. Its movement is autobiographical before becoming theoretical: Hayek traces his early psychological investigations, reformulates neural classification through the concept of disposition, and concludes by examining the limits of explanation. The central claim is that mental qualities arise from the relational organization of neural activity, rather than being properties carried by individual sensory impulses. His retrospective clarification makes this organization an ongoing process whose changing dispositions shape both perception and action.

The opening account locates Hayek’s psychological education in the absence of effective teaching at postwar Vienna. His interlocutors were principally books by earlier psychologists and physiologists, especially Helmholtz and Mach. Mach supplied the decisive stimulus, but Hayek rejected the assumption of elementary sensations possessing an intrinsic qualitative core. If acquired connections could explain some attributes of sensation, perhaps their place within a system could explain every mental quality. This yielded two ways of ordering the same events: the physical order investigated by science and the sensory order through which organisms encounter their surroundings.

My conclusion at an early stage was thus that mental events are a particular order of physical events within a subsystem of the physical world that relates the larger subsystem of the world that we call an organism (and of which they are a part) with the whole system so as to enable that organism to survive.

Mental order is therefore neither a separate substance nor a transparent reproduction of physical reality. It is an imperfect, generic map that helps an organism survive. Hayek’s immediate explanatory target was the system of sensory qualities, but his ambition extended to emotions, concepts, images, and drives. The autobiographical interruption matters here: economics displaced psychology as his profession, while his later critique of “scientism” helped clarify what an explanation of complex phenomena could legitimately accomplish. His recognition of markets as information-communicating mechanisms appears as a related intellectual development, rather than as a substitute for the psychological argument.

Returning to his manuscript around 1946, Hayek found the theoretical problem largely unresolved. He accepted that mental attributes could be distinguished through their effects as guides to action, but rejected the behaviorist shortcut from stimulus to observable conduct. Conduct was the eventual outcome of an internal process requiring reconstruction. The central nervous system instead performs continuous classification and reclassification at multiple levels; an impulse acquires significance through its relations to other impulses and their possible consequences.

Rereading the book for the conference, Hayek discovers that the term he now considers central—“disposition”—had received surprisingly little emphasis. This acknowledgment distinguishes his current formulation from a simple restatement of the earlier book.

It seems to me now that I could have greatly simplified my exposition in the book if I had throughout used the term disposition.

Dispositions encompass much more than readiness to move. They include tendencies to interpret subsequent stimuli, to alter other dispositions, and to enter long sequences whose eventual actions may remain merely possible. Physiological “linkages,” established through previous simultaneous activity, generate the “followings” of impulses. Their overlapping effects determine which further neurons fire. These connections constitute mental contents; they are not associations between contents already independently formed.

Hayek accordingly replaces the picture of isolated responses with a continuing neural flow. New stimuli redirect an already active system whose state determines how they are interpreted. He cautions that diagrams of branching connections can misleadingly suggest spatially localized groupings: the relevant ramifications may extend throughout the cortex. Widespread transmission also need not produce an indefinitely expanding number of excited neurons. His analogy with a capital stock emphasizes an enduring organization nourished by inputs and producing outputs, rather than a sequence beginning afresh with each stimulus.

The final philosophical discussion returns to the contrast between physical and sensory classification. Physics revises the classifications supplied by perception to explain regularities more adequately; theoretical psychology explains why physically ordered events produce a different order in experience. Hayek regards their relationship as explicable in principle, but never exhaustively by the human mind.

The proof I have attempted in my book that any explanation—which always rests on classification—is limited by the fact that any apparatus of classification must be of a higher degree of complexity than what it classifies, and that therefore the human brain can never fully explain itself, may be inadequate.

This qualification is essential: Hayek presents a consequential argument whose strict proof remains uncertain, not an established theorem. His comparison with Gödel indicates the difficulty and intended reach of the claim. He allows that a substantially more complex brain might explain ours physiologically, while resisting absolute assertions about whether separate mental and physical worlds “exist.”

The mechanical-rat example makes the distinction between understanding a mechanism and predicting its behavior concrete. Even a perfectly known artificial rat would encounter stimuli and undergo internal classifications beyond our capacity to reproduce mentally. Exact prediction would require an identical mechanism with an identical history—in effect, another rat. The implication for understanding people is a principled limit on exhaustive prediction, not the abandonment of causal explanation. Hayek closes by welcoming cognitive psychology as a field capable of situating meaning within the physical world:

It seems to me that the young discipline of cognitive psychology is succeeding in showing that “meaning” can be given a meaningful place in our picture of the physical world.