Kirzner’s four-chapter monograph reconstructs capital theory around individual decisions and the coordination of production plans through time. Engaging Böhm-Bawerk, Mises, Hayek, Lachmann, and their critics, it treats capital goods as elements of purposeful, revisable activity rather than as a homogeneous fund automatically yielding income. This approach connects capital theory to entrepreneurial expectations, error, and adjustment, extending its significance beyond the explanation of interest.
The opening chapter, “Unfinished Plans,” moves from Crusoe’s isolated production decisions to overlapping projects and interacting market plans. Capital goods derive their economic significance from undertakings already begun but not completed. Kirzner describes the decision-maker’s intermediate position:
He has already performed some of the actions initially called for by his multi-period plan, and he now has before him a program of further actions, prescribed by the plan for its subsequent stages.
An oven, a plowed field, or accumulated provisions reflects earlier intentions while providing opportunities for subsequent choices. Physical properties constrain uses without determining economic function. Past decisions explain why particular resources exist, but present expectations govern whether their original uses remain worthwhile. In a market economy, independently formulated plans may conflict. Losses for an oven manufacturer can coexist with profitable use of cheaply acquired ovens by bakers. Explaining adjustment requires attention to inherited equipment without assuming that the plans responsible for producing it were correct.
“Stocks and Flows” challenges accounts that locate capital’s productive contribution in its mere presence. Dividing production into arbitrary intervals can obscure the acquisition, use, and replacement decisions contained in a multi-period plan. A production function relevant to economic explanation must represent alternatives confronting a chooser, not merely a technological relationship observed over a selected interval. This distinction also separates sunk expenditures from costs relevant to present action.
Knight’s conception of permanent capital receives particular criticism. Treating capital as a perpetual income source presupposes the reinvestment decisions that theory should explain. Constancy is a possible objective, not an automatic property of accumulated equipment:
If Crusoe is interested in maintaining a constant level of consumption, then he must plan his actions to this end.
Kirzner nevertheless retains capital-income distinctions for accounting. His objection is to making accounting categories explanatory without specifying the choices behind them. Maintaining consumption or income requires a criterion of constancy; comparisons of satisfaction across dates do not supply an objective standard independently of individual valuation.
“Capital and Waiting” shifts attention from elapsed production time to the delay anticipated by prospective decision-makers. Stationary production does not eliminate choices between present consumption and provision for the future. Aggregate inflows and outflows may occur simultaneously while individual plans still involve postponement. Kirzner criticizes mechanical stock-flow treatments, including Dorfman’s reconstruction of Austrian theory, when they substitute historical detention periods for prospective choices and time preference.
The chapter distinguishes capital as the result of past waiting, as resources permitting further waiting, and as completed preliminary work that shortens the remaining route to a desired result. These perspectives do not establish waiting as an independently necessary productive input. The timing of output already enters the chooser’s appraisal of a plan.
“Measuring Capital” examines heterogeneity, quality change, valuation, cost, and durability. Backward-looking aggregation cannot straightforwardly combine subjective sacrifices made at different dates under different valuations. Forward-looking valuation is meaningful for an individual, but depends on expected prices, complementary resources, and a particular production plan. Monetary expression can conceal precisely the differences that matter for explaining production:
But this heterogeneity is completely submerged when assets are expressed as a value of money.
Nor does adding individual valuations necessarily produce a coherent social capital quantity: underlying expectations and plans may be mutually inconsistent. An integrated aggregate can therefore assume away the coordination problem that capital theory ought to investigate. Kirzner allows qualified uses for measurement while resisting its elevation into a universal foundation of explanation. His central contribution is to connect capital heterogeneity with unfinished action: inherited resources matter through the opportunities they offer to agents who must assess, complete, or revise their plans.
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