"To Ehrenfest I owe a great deal. I studied physics at a time when a number of fascinating persons were there together. Ehrenfest would not instruct as such, as he preferred dialogue. Thanks to him I could participate in discussions with Albert Einstein. Also Kamerling Onnes, Lorentz and Zeeman were present. Being a student in the hands of such teachers, you are very fortunate indeed."

“It is my hope that in such a way we may again, as Marx claimed, find scientific arguments in the competition between various systems, but up-to-date scientific arguments rather than obsolete ones. This more fundamental research in economics deserves relatively more attention and resources than the more superficial versions of economic research directed at forecasting or analysing very short-term fluctuations in market prices, on which quite some money is being spent to-day.”

“An inequality-furthering phenomenon is technological development. But need it be? Increasingly we get the feeling that technological development is not simply something given, but that it may be guided, within limits.”

“The world is in a process of a great transformation. In a considerable part of it a new economic order, "communism," is being vigorously tried out. Elsewhere an old order is passing as one country after another throws of the yoke of colonialism. The wholesale introduction of Western techniques and ways of life shaking the foundations of numerous beliefs and attitudes, for good and for evil.”

“The dominant role played by... exporters’ and importers’ GNP and distance in explaining trade flows.”

“The shaping or reformulation of the aims of economic policy which are only vaguely felt may be exemplified in the aim of social justice.”

“The main sources of tension in today's world economy could be grouped under the following categories:”