In 2001 Indonesia possessed the largest Muslim population of any country in the world. Between 85 and 90 percent of the population of more than 180 million is Muslim, mostly Sunnis who adhere to the Shafii school of Islamic law. Islam arrived in the thirteenth century and was the majority religion by the eighteenth century. Conversions occurred mainly through peaceful means, via traders accompanied by religious scholars and Sufis. Sufism and the general tolerance of local traditions aided the growth of Islam and accounts for Hindu and other non-Muslim elements in Islamic practices. The nineteenth and early twentieth centuries saw the rise of reformism, particularly criticism of non-Islamic elements of religious faith and practice. In the twentieth century, Islam provided a common sense of identity in the face of European colonialism and an ethnically and linguistically diverse population. Pancasila (the Five Principles) was proclaimed as the national ideology after 1945, reflecting a secular and pluralist view of the role of religion in the state. The 1960s witnessed the proliferation of missionary activities and the rise of Islamism. Beginning in the late 1970s, radical Muslims turned to violence to express opposition to the government, seeking a stronger role for Islam in Indonesian politics. This, combined with increasing antagonism over the perceived power of Christianity in the islands, led to the 1999 election of Abdurrahman Wahid, who promised to end violence and assert a stronger presence of Islam in government, a position he held until 2001, when he was forced from office by the parliament that had elected him.