"As the title of his 1941 book indicates, the theory of capital lay at the heart of his theory of the cycle. The reason is that he attributes the cycle not to changes in aggregate demand, or even to changes in the quantity of capital, but to changes in the structure of production and hence the structure of the capital stock. In this, his theory was highly unusual: one of the reasons for his failure to engage more effectively with Keynes was the latter’s inability to see how the theory of capital could be of any importance for the cycle. Because the theory of capital is so central, and because it is so complex, it needs to be explained carefully. After that, the rest of his theory falls into place comparatively easily."

“Following the financial crisis of September 2008 when the American investment bank Lehman Brothers collapsed, threatening to engulf the entire banking system, the British economist John Maynard Keynes returned to center stage. In the popular press and in the writings of many economists, Keynes featured prominently as governments around the world urgently sought ways to avoid economic collapse. After only a brief delay, critics of Keynes’s ideas also began to appear; but the emergence of such critics only served to emphasize the fact of his return, for only a few years earlier Keynes’s name would not even have appeared in public debate about economic policy: his ideas were seen as having so little relevance that it did not even seem necessary to mention his name when discussing the performance of the economy.”

“In the years after 1936, whilst Hayek was working on The Pure Theory of Capital, most economists were convinced by Keynes, whose theory had an elegance and simplicity that Hayek’s did not. Keynes’ theory lacked Hayek’s theoretical rigor in that it was not based on equilibrium , and there were places in the argument where Keynes relied on loose, informal arguments, preferring to put his trust in intuition rather than formal theory. Keynesians did not solve the problems with capital theory that Hayek had identified: they just bypassed or ignored them. According to Hayek’s methodological criteria, Keynes’ theory was decidedly inferior. Against this, Keynes’ theory provided opportunities for mathematical and statistical analysis that Hayek’s did not. Indeed, though Hayek paid some attention to data, he did so only minimally: he certainly made no attempt to test his theory against statistical data. The choice of Keynesian theory was, at least in part, a methodological one.”

“Since the 1970s, interest in economic methodology has grown dramatically, to the extent that it is now possible to view methodology as a clearly identifiable sub-discipline within economics.”