Friedrich A. Hayek, “Degrees of Explanation” (1967)

This file is a single methodological essay in philosophy of science, reprinted from the British Journal for the Philosophy of Science. Its scope is the logic of explanation in complex phenomena—biology, geophysics, economics, and other social sciences. Hayek’s main thesis is that the ideal of exact prediction modelled on classical physics is only one kind, and one degree, of scientific understanding.

The discussion of scientific method has been guided almost entirely by the example of classical physics.

Hayek begins by accepting much of Popper’s hypothetico-deductive view: scientific theories are deductive systems whose consequences forbid certain events and can be falsified, not inductively verified. But he rejects the inference that science must always discover new laws yielding precise predictions. Even in applied physical disciplines, much theoretical work selects accepted laws and combines them into patterns suited to tides, earthquakes, weather, or other complex situations. In more complex fields, the physics template becomes misleading because the relevant variables cannot all be observed, controlled, or computed.

There is no guarantee that we shall ever be able, physically or conceptually, to handle phenomena of any degree of complexity, nor that phenomena of a degree of complexity exceeding this limit may not be very important.

The essay’s middle sections redefine prediction by degrees. A prediction need not specify a unique event at a precise place and time; it may narrow a range, state a disjunction, or exclude an outcome. This move lets Hayek preserve empirical discipline without demanding impossible precision. Explanation and prediction remain connected because both use general rules to delimit what may happen, but the strength of the delimitation varies with the complexity of the subject.

A statement which excludes only one of all conceivable events from the range of those which may occur is no less a prediction and as such may prove to be false.

The core conceptual move is the explanation of the principle. Instead of moving from an unknown hypothesis to a known observation, the investigator begins with familiar mechanisms and asks whether their combined operation can account for a complex pattern. Such an explanation is tested less by measuring every element than by seeing whether the postulated mechanism makes some combinations possible and others impossible. Hayek’s chief natural-science example is evolution by natural selection: its premises are not usually in doubt; the problem is whether they suffice to order known facts and exclude biological impossibilities.

It will thus give us new information by indicating the range of phenomena to expect.

His discussion of models generalizes the same point. Formal or verbal models may be explanatory even when the values of their variables cannot be ascertained, because they describe a structure of admissible relations. This is why biology and economics can yield real knowledge without exact forecasts: they explain patterns, ranges, and incompatibilities. A model’s value lies not only in calculation but in its power to show what a type of mechanism could generate.

Any model defines a certain range of phenomena which can be produced by the type of situation which it represents.

In the social sciences this yields mainly negative or pattern predictions. Economics often tells us that certain aims cannot be jointly achieved: fixed prices cannot clear all increased demand; some monetary and exchange-rate policies are mutually inconsistent; certain institutions presuppose attitudes that make other institutions unlikely. Hayek’s practical point is not resignation but discipline: theory keeps action from pursuing mutually defeating ends.

The practical value of such knowledge consists indeed largely in that it protects us from striving for incompatible aims.

The final section names the appropriate stance toward complex orders as orientation rather than detailed forecast, and cultivation rather than control. Hayek stresses that explanations of principle are weaker than full explanations where full explanations are possible, but stronger than silence where detailed prediction is unattainable. The essay’s enduring relevance is its defense of scientific modesty about complex systems: neither scientistic control nor positivist dismissal is adequate to biology, culture, markets, or institutions.

It is certainly not helpful to discredit what may be the only sort of knowledge we can achieve in these fields.