The object of our analysis is, not to provide a machine, or method of blind manipulation, which will furnish an infallible answer, but to provide ourselves with an organized and orderly method of thinking out particular problems; and, after we have reached a provisional conclusion by isolating the complicating factors one by one, we then have to go back on ourselves and allow, as well as we can, for the probable interactions of factors amongst themselves. This is the nature of economic thinking. Any other way of applying our formal principles of thought … will lead us into error.

To me, the most extraordinary thing regarded historically, is the disappearance of the theory of demand and supply for output as a whole, i.e. the theory of employment, after it had been for a quarter of a century the most discussed thing in economics. One of the most important transitions for me, after my Treatise on Money had been published, was suddenly realizing this.