What constitutes the barriers to demand against which the accumulation of capital collides in periods of crisis or stagnation? The prevailing Marxist common sense suggests that such barriers derive from the limited purchasing power of the wage. The author takes issue with this common sense in order to prepare the way for a more adequate answer to the question posed. As analysis of the practical logic of exchange reveals, under capitalist conditions the ultimate source of all effective demand in the economy is the capitalist class itself.