Sidney Alexander graduated from Harvard in 1936 and spent the subsequent year studying in the UK with John Maynard Keynes at King’s College, Cambridge. Returning to the US, he worked with the NBER and then with the OSS during the war. His 1946 doctorate was on the financial structure of American corporations. Paul Samuelson, one of his close colleagues at MIT, grouped Sidney in the generation of the “Golden Days of Harvard Yard”. After the war, Alexander contributed to work on the Marshall Plan and later joined the IMF, where his notable contribution was to its econometric work and the development of the absorption approach to the balance of payments. He worked in business as Economic Advisor to CBS before joining the Sloan School of Management at MIT in 1956 as Professor of Industrial Management. Alexander’s great skill was in applying his ability with statistics and mathematical economics with an astute grasp of geopolitics. In the rapidly changing environment from the 1940s to the 1970s he provided, to government, business and students alike, what he hoped the economist could, an insightful “window upon the world”.