Friedrich August von Hayek, The Mythology of Capital (1936)

Hayek’s journal article is a six-part intervention in his controversy with Frank H. Knight over capital, investment, and interest. Its central objection is to treating capital as a permanent fund that maintains itself independently of the particular goods composing it. Capital goods wear out, and their replacement requires economic decisions: continuity of income is something to explain, not an assumption that makes explanation unnecessary. Hayek also rejects the Austrian simplification of capital into a single or average period of production. His aim is to preserve the importance of time while abandoning the homogeneous fund that both Knight and earlier Austrian accounts, in different ways, presuppose.

The opening section distinguishes this disagreement from questions on which Hayek admires Knight’s work, especially the relationship between productivity and time preference in determining interest. The disputed issue is whether replacement can be relegated to a technological detail and production treated as simultaneous with consumption. For Hayek, such claims obscure how a limited stock of capital restricts the choice among known productive methods. An increase in capital, he argues, makes possible longer investment of some resources; identifying those resources and their prospective returns is essential to explaining what additional capital accomplishes.

Section II clears away six misconceptions about this argument. Hayek holds technical knowledge constant, separating capital-enabled increases in output from invention. He distinguishes the investment periods of particular factors from the production cycle of a particular commodity: resources may move into industries with longer investment periods without any industry changing its technique. Neither a measurable aggregate waiting period nor an average period is necessary to establish this relationship. Nor does the argument depend on tracing products back to original factors, distinguishing primary from produced resources, or assuming that intermediate goods have only one possible use.

What is essential is solely that whenever a change occurs in any part of the economic system which involves that more (or less) capital is used in the industry or industries concerned, this always means that some of the factors used there will now bring a return only after a longer (or shorter) time interval than was the case in their former use.

The relevant comparison concerns future returns from alternative present uses, not the historical labor embodied in existing goods. Durable equipment introduces a further complication: its physical service life does not by itself establish how the invested resources should be attributed to successive services. That attribution requires valuation. Hayek’s time analysis therefore does not offer a purely technical measure of capital independent of prices and interest.

Section III applies these distinctions to Knight’s agricultural examples. More crops of the same growth period, or additional crops with shorter growth periods, do not demonstrate that new capital can raise output without extending investment. Hayek asks why these changes require new saving at all. If labor shifts from current production into making equipment, or moves from a shorter investment into a longer one, consumption temporarily falls below what the resources could otherwise provide. Saving bridges that gap. An unchanged crop cycle consequently tells us little about the changed investment periods of the resources supporting it.

The fourth and longest section develops the positive conceptual alternative. Existing capital goods cannot generally be equated with a fixed subsistence fund: their combinations with other resources permit different future streams of consumption, varying in amount, composition, and timing.

The role of the existing capital goods in this connection is that they fill the gap in the income stream which would otherwise have been caused by the investment of resources which might have been used to satisfy current needs.

Replacement is thus a coordination of income streams, not the migration of an enduring substance from old equipment into new. Existing goods sustain consumption while current resources are invested to produce their successors. Whether this succeeds depends jointly on the temporary support those goods provide and the increased returns obtainable through waiting. Hayek criticizes Böhm-Bawerk’s fixed subsistence fund alongside Knight’s permanent capital: neither captures the alternative uses of heterogeneous equipment. He explicitly reserves the full technical apparatus for a systematic study, noting the difficulty of joint-product and joint-demand relationships across time.

Section V tests Knight’s framework against his assertion that zero interest would require all capital-assisted products to become free goods. Hayek distinguishes the return to waiting from the scarcity value of reproducible equipment. If further extensions of investment no longer increase output, additional saving cannot increase production; nevertheless, replacement still requires scarce resources.

So long as any of the factors required for this purpose remain scarce, the capital goods themselves and a fortiori the final consumers' goods made with their help will also remain scarce.

The argument establishes a theoretical possibility, not a prediction of imminent zero interest. Truly permanent useful goods present a different limiting case, but their valuation cannot determine that of goods requiring reproduction.

The final section considers perfect foresight. A plan correctly anticipating everything from the beginning would remove subsequent problems of replacement and redeployment. It would not explain adjustment in an economy continually encountering unforeseen circumstances.

Economic problems of any sort, and in particular the problem of how to use a given stock of capital goods most profitably, arise only when it is a question of adjusting the available means to any new situation.

The article’s relevance to economic dynamics and industrial fluctuations lies here. The pertinent supply of capital comprises the alternative income streams existing goods can yield under changed conditions, not a constant quantity guaranteed by perfect foresight. Treating invested capital as completely mobile suppresses the constraints needing explanation. Hayek’s central move is to replace an abstract capital substance with an analysis of heterogeneous goods, waiting, valuation, and the coordination of consumption through time.