From the article:

It is a central starting point for Marglin that Keynes's assertion that a self-regulated capitalist economy will not gravitate to full employment cannot be proven on the basis of static analysis or comparative-static equilibrium considerations. Rather, a genuine dynamic analysis is required that goes beyond the “correspondence principle” developed by Samuelson. So the core of Marglin’s reformulation of the Keynesian approach consists of two assumptions that are essential for the dynamic adjustment problem. They concern, on the one hand, the relative adjustment rates of money wages and prices on labour and goods markets and, on the other hand, the question of how entrepreneurs react to the dual signals outside equilibrium in their decisions on production quantities and pricing. The application of a dynamic analysis would make it clear that the core of Keynesian theory is not the emphasis on nominal rigidities, but rather the emphasis on the importance of aggregate demand, which also applies when eliminating such rigidities, i.e. in a flexprice economy.