Feasible but not viable

After quoting James Buchanan on general equilibrium (see yesterday's post) Peter J. Boettke expands on the thought, saying

This is how the price system impresses upon decision makers the essential items of knowledge required for plan coordination. This is how monetary calculation works to guide us amid a sea of economic possibilities and ensures that among the technologically feasible only the economically viable projects are selected.

Chicago Tribune 14 April 1945

I read that far, and a TOYNBEE flag went off in my head. Among the technologically feasible, only the economically viable projects are selected, Boettke says. Yeh. Only the economically viable.

Toynbee, Arnold J. Toynbee, said the construction of roads and viaducts was abandoned after the fall of Rome because, though such projects were still technologically feasible, they were no longer economically viable.

Note that in the Chicago Tribune story from 1945, Toynbee is quoted as saying "Social malady was the cause" of the abandonment of Roman roads. But he also points out that "a road system of the Roman standard would not have paid its way". Would not have paid its way. In other words, not economically viable.

There is one additional sentence in Peter Boettke's paragraph:

... among the technologically feasible only the economically viable projects are selected. This is how wealth is created and humanity is lifted from the miserable condition of extreme poverty to one where human flourishing is even possible.

Yeah, "humanity is lifted from the miserable condition" because economically viable projects are selected. But it doesn't work all the time. When Roman roads stopped being viable, they stopped being built. But choosing a less un-viable alternative did not "lift humanity from the miserable condition." It only slowed the descent toward misery.

Peter Boettke suggests that the market system drives us to the economically viable. I can see that. But the economically viable option is not sure to "lift humanity". Most often, perhaps it does. In the decline phase of the cycle of civilization, it does not.