Kenneth J. Arrow (1921–2017)
Kenneth Arrow was the doyen of economic theory during the second half of the twentieth century. His fundamental and diverse contributions — to fields including welfare economics, which aims to evaluate social welfare on the basis of individual choices or preferences — were founded on abstract reasoning and remarkably few elementary mathematical concepts. [...]The crown jewel of mathematical politics is Arrow's impossibility theorem — the demonstration that collective decision-making based on the choices of individuals cannot produce results that reflect the preferences of society as a whole." Full obituary @ Nature.