It took some searching, but I found one economist who isn't a complete idiot on the subject of secular stagnation and biophysical limits. This paper sheds some more light on the theoretical assumptions being made by Summers and Krugman, plus adds a dose of peak oil
Secular Stagnation and the Failed Growth Economy [PDF] by Kent Klitgaard, Professor of Economics, Wells College
I added some paragraph breaks to deal with the text wall
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')Economic Growth is the Holy Grail of mainstream macroeconomic theory. Although a focus on accumulation has existed since the inception of economics as a discipline, the current emphasis on growth was developed in the years following the Great Depression of the 1930s. Growth developed as an explicit strategy to meet the social need for employment and an increase in material standards of living without
confronting the politically unpopular (at least in the United States) strategy of income redistribution from the wealthy to the poor.
Unfortunately the growth economy is subject to three sets of limits, and there is increasing evidence that human economies are presently facing these limits. The first set of limits are internal and are found in the dynamics of capital accumulation, specifically as regards investment. When these limits are reached the economy stagnates, either cyclically or over the long term (secularly).
A second set of biophysical limits exist, manifest on the supply side as peak oil and on the sustainability or assimilation side as human induced climate change. In addition a host of other adverse growth-generated phenomena such as mass extinction, acidification of the oceans, and an ecological footprint that exceeds biocapacity are appearing on a world scale.
A final set of limits exists in the political process. The post World War II years in the United States witnessed the construction of a series of growth coalitions, whose political agendas of acquiring more for their constituents required economic growth to maintain their legitimacy. As the capacity for growth declines so too does the ability to grow one’s way out of social dilemmas. The inability to grow compromises business-as-usual politics as well as economics.
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When long-term strategies for growth succumb to internal or biophysical limits they do not immediately give way to superior strategies. Instead the nation often becomes mired in a period of political impasse. The twentieth century in the United States was dominated by periods of impasse. The accepted vision of the self-regulating economy was dashed by the severity of the great depression, and after nearly half a decade a new vision emerged in the form of the New Deal. This vision of a managed economy and a positive state survived until the limits of effectiveness were reached in the early 1970s.
The liberal growth agenda, driven by increasing household incomes, could not survive the peak of US oil production, the beginning of the decline of US political power, and the onset of stagflation. A long period of impasse followed, only broken in the early 1980s with the election of Ronald Reagan to the presidency and the implementation of a conservative (neoliberal) growth agenda grounded in the reduction of production costs and the expansion of unregulated financial markets.
We are currently witnessing another such period of political impasse. Unregulated financial markets collapsed in a global financial meltdown in 2008. However providers of financial services are not yet ready to abandon business as usual. A restructuring of global rules languishes as the pressure on economies of the Eurozone to reduce debt threatens, once again, the stability of the world economy.
The result of the historical conjuncture of these limits results in The Failed Growth Economy: an economy that must produce growth in order to provide for profits and employment yet at the same time simply cannot produce this requisite growth.
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So the coming of peak oil may have the same type of dual effect that Domar posed as a problem as regards investment. If a country adapts an easy money policy the risk of system-wide financial collapse increases as does the marketing of increasing quantities of lower quality securities spreads. If the nation runs a contractionary monetary policy the risk of stagflation becomes more probable. Furthermore, especially in the United States, peak oil threatens the demand side of the equation by reducing discretionary income....
Clearly the intersection of internal and biophysical limits will impact not only the growth possibilities of the system but also adversely affect the lives of everyday citizens, especially the most vulnerable.