From the inroduction:

Stephen Marglin, in his chapter, "Keynes in the long run: Growth with unlimited supplies of labour", acknowledges that a Keynesian 'long run' will seem to some an oxymoron, as a long-standing mainstream consensus hands over the short run to Keynes but reserves the long run for neoclassical orthodoxy. Marglin's opinion is that Keynes always intended something more than a novel explanation of sand in the wheels which temporarily impede the invisible hand's ability to clear the labour market. In the present contribution, his intention is to build a long-run model on the basis of the fundamental Keynesian insight, namely the absence of an efficacious mechanism by which the labour market adjusts to an equilibrium without unemployment and, in consequence, a role for demand in determining not only the composition of output but also its level. Marglin brings in insights from other perspectives, particularly the Marxian notion of a 'reserve army' of workers available for mobilisation by capitalists. In the conclusion, he speculates over whether, in the future, capitalism will still be able to draw on virtually unlimited supplies of labour, as ecological considerations introduce considerable uncertainty about whether the planet can sustain growth on the scale that has become the norm.