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I note in passing that there is again some dispute of the near-tautological principle of comparative advantage, but also some far more interesting discussion (in part by one Migeru) of whether its consequences are still as had been expected.

In the pernicious-idea category (and more peripheral to the diary) is the expensive-energy => near-autarky idea. Shipping, however, is now at the few-cents per ton-mile level, and a moderate multiplier on that cost would be far from being a barrier to international trade, though it would of course reduce it at a significant margin.
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As a Wikipedia addict and occasional contributor, I find that:

According to Lassalle, wages cannot fall below subsistence level because without subsistence laborers will be unable to work for long. However, competition between laborers for employment will drive wages down to this minimal level.
Iron law of wages

Later, Ricardo said:

"Notwithstanding the tendency of wages to conform to their natural rate, their market rate may, in an improving society, for an indefinite period, be constantly above it; for no sooner may the impulse, which an increased capital gives to a new demand for labour, be obeyed, than another increase of capital may produce the same effect; and thus, if the increase of capital be gradual and constant, the demand for labour may give a continued stimulus to an increase of people...." (On the Pinciples of Political Economy, Chapter 5, On Wages).
Iron law of wages

This sounds more like a Plastic Law of Wages.

I would like to propose a Silicate Law of Capital, which states that as the human ability to transform matter increases, the cost of capital goods will fall to a level not significantly above that of the free energy consumed in its fabrication and the matter tied up in its physical structure. (Iron will not be a preferred structural material, as silicates are both more abundant and can be made stronger, owing to their directional covalent bonds.)

Malthus, however, still bites. Exponential growth of population (and no, the demographic transition isn't enough to show that this won't happen) would eventually reduce free energy flows per capita to a minimal level. Potential checks against this will include the traditional death option, or the more avant-garde option of part-time living (technology pending).

Words and ideas I offer here may be used freely and without attribution.