Heterogeneity of Capital Means Heterogeneity in Use; Heterogeneity in Use Implies Multiple Specificity

All capital resources are heterogeneous. The heterogeneity which matters is here, of course, not physical heterogeneity, but heterogeneity in use. Even if, at some future date, some miraculous substance were invented, a very light metal perhaps, which it was found profitable to substitute for all steel, wood, copper, etc., so that all capital equipment were to be made from it, this would in no way affect our problem. The real economic significance of the heterogeneity of capital lies in the fact that each capital good can only be used for a limited number of purposes. We shall speak of the multiple specificity of capital goods.

—Ludwig M. Lachmann, Capital and Its Structure (Kansas City: Sheed Andrews and McMeel, 1978), 2.

“Complementarity” Is of the Essence of Capital Use; the Entrepreneur Has to Find the “Optimum Combination”

It is hard to imagine any capital resource which by itself, operated by human labour but without the use of other capital resources, could turn out any output at all. For most purposes capital goods have to be used jointly. Complementarity is of the essence of capital use. But the heterogeneous capital resources do not lend themselves to combination in any arbitrary fashion. For any given number of them only certain modes of complementarity are technically possible, and only a few of these are economically significant. It is among the latter that the entrepreneur has to find the ‘optimum combination.’ The ‘best’ mode of complementarity is thus not a ‘datum.’ It is in no way ‘given’ to the entrepreneur who, on the contrary, as a rule has to spend a good deal of time and effort in finding out what it is. Even where he succeeds quickly he will not enjoy his achievement for long, as sooner or later circumstances will begin to change again.

—Ludwig M. Lachmann, Capital and Its Structure (Kansas City: Sheed Andrews and McMeel, 1978), 3.