Karl Popper, known for his concept of falsifiability in the philosophy of science, also was a somewhat influential political thinker in his time. Popper endorsed what he called "the Open Society," a liberal democratic society based on abstract and depersonalized material connections, instead of direct social relationships. This vision was particularly influential on one of Popper's now famous students, George Soros, who would go on to use his significant wealth won in financial markets to found the Open Society Foundation, a significant source of funds for leftist political agitation and pressure in America and Europe. Soros's worldview has somewhat departed from Popper's, with an emphasis on what Soros calls reflexivity, the principle that in human domains, our theories of world affect the world itself.