Perhaps the most prominent exponent of spontaneous order is Friedrich Hayek. In addition to arguing the economy is a spontaneous order, which he termed a catallaxy, he argued that common law and the brain are also types of spontaneous orders. In "The Republic of Science," Michael Polanyi also argued that science is a spontaneous order, a theory further developed by Bill Butos and Thomas McQuade in a variety of papers. Gus DiZerega has argued that democracy is the spontaneous order form of government, David Emmanuel Andersson has argued that religion in places like the United States is a spontaneous order, and Troy Camplin argues that artistic and literary production are spontaneous orders. Paul Krugman too has contributed to spontaneous order theory in his book "The Self-Organizing Economy", in which he claims that cities are self-organizing systems. Credibility thesis suggests that the credibility of social institutions is the driving factor behind the endogenous self-organization of institutions and their persistence.