In section 13.1, Keynes argues that, according to this new general theory, the rate of investment varies to the effect of equilibrating the marginal efficiency of capital (i.e. relation of prospective yield of capital equipment to supply cost) to the given interest rate. This relationship between the marginal efficiency of capital and the interest rate, he has referred to already as the schedule of the marginal efficiency of capital. Here, he says that this schedule exerts a causal force on the investment levels (i.e. that portion of proceeds earned from output, beyond consumption).
unresolved He also argues that the classical view on this subject does not hold up to scrutiny, but I don’t understand how he frames the classical theory in this section.