"I remember Robbins asking me if I could turn the Hayek model into mathematics... it began to dawn on me that... the model must be better specified. It was claimed that, if there were no monetary disturbance, the system would remain in 'equilibrium'. What could such an equilibrium mean? This, as it turned out, was a very deep question; I could do no more, in 1932, than make a start at answering it. I began by looking at what had been said by... Pareto and Wicksell. Their equilibrium was a static equilibrium, in which neither prices nor outputs were changing... That, clearly, would not do for Hayek. His 'equilibrium' must be progressive equilibrium, in which real wages, in particular, would be rising, so relative prices could not remain unchange … The next step in my thinking, was … equilibrium with perfect foresight. Investment of capital, to yield its fruit in the future, must be based on expectations, of opportunities in the future. When I put this to Hayek, he told me that this was indeed the direction in which he had been thinking. Hayek gave me a copy of a paper on 'intertemporal equilibrium', which he had written some years before his arrival in London; the conditions for a perfect foresight equilibrium were there set out in a very sophisticated manner."

“Hayek was making us think of the productive process as a process in time, inputs coming before outputs.”

“So long as we confine our attention to income from property, and leave out of account any increment or decrement in the value of prospects due to changes in people's own earning power , Income No. 1 ex post is not a subjective affair, like other kinds of income; it is almost completely objective.”

“The standard stream corresponding to Income No. 3 is constant in real terms... We ask... how much he would be receiving if he were getting a standard stream of the same present value as his actual expected receipts. This amount is his income.”

“I did not begin from Keynes: I began from Pareto, and Hayek.”

“We must give the system sufficient factors of stability to enable it to work; but we must not assume that these forces are so powerful as to prevent the system from being liable to fluctuations. There must be a tendency to rigidity of certain prices, particularly wage-rates; but there must also be a tendency to rigidity of certain price-expectations as well, in order to provide an explanation for the rigidity of these prices... Indeed we should do better to assume a good deal of variation in different people’s elasticities of expectations... Of course the way in which a population is divided with respect to this sort of sensitivity will vary very much in different circumstances... We have to be prepared to deal with a range of possible cases, varying from that of a settled community, which has been accustomed to steady conditions in the past , to that of a community which has been exposed to violent disturbances of prices (and which may have to be regarded, in consequence, as being economically neurotic.”

“There is much of economic theory which is pursued for no better reason than its intellectual attraction; it is a good game. We have no reason to be ashamed of that, since the same would hold for many branches of pure mathematics.”