Criticism of Islam has existed since Islam's formative stages. Early written criticism came from Christians, prior to 1000 AD, many of whom viewed Islam as a radical Christian heresy. Later there appeared criticism from the Muslim world itself, and also from Jewish writers and from ecclesiastical Christians. In the modern era, criticism has come from Hindus, Sikhs, Jains, most notably atheists, as well as people both inside and outside Islam, on a wide variety of topics.