The URC is governed by a combined form of congregationalism and presbyterian polity. It is a principle of congregationalism that ministers do not govern congregations by themselves. Its organizational pattern is a kind of modified congregationalism. The Cambridge Synod was called in response to these attacks on Congregationalism. He also became the spokesman for the new church polity known as Congregationalism. There is no other reference than the local congregation for the "visible church" in Congregationalism. The term used by supporters at the time was "large Congregationalism". Spurgeon's conversion from nominal Congregationalism came on 6 January 1850, at age 15. In 1837, Williams converted from Anglicanism to Congregationalism. Congregationalism is not limited only to organization of Christian church congregations. The two foundational tenets of Congregationalism are "sola scriptura" and the priesthood of believers. As a Presbyterian minister, Baillie was critical of Congregationalism and targeted Cotton in his writings. Cromwell and many others in the army supported congregationalism. Congregationalism was the established religion supported by public taxation. In congregationalism, rather uniquely, the church is understood to be a truly voluntary association.