Criticism of religious belief

The most widely known Western criticism of religious constructs and their social consequences has come from atheists and agnostics. Anti-Catholic/anti-Christian sentiment first gathered force during the 18th century European Enlightenment through pioneering critics such as Voltaire and his fellow Encyclopedists, who were for the most part deists. The French Revolution then instituted what later became known as secularism, a constitutional declaration of the separation of church and state. In addition to being adopted by the new French and United States republics, secularism soon came to be adopted by a number of nation states, both revolutionary and post-colonial. Marx famously declared religion to be the "opium of the people".[36] This conception was applied in the state atheism of social systems inspired by Marx's writings, most notably in the Soviet Union and China, and most notoriously in Cambodia, although Marx himself believed that religion would disappear by itself once the perceived social ills of capitalism were eliminated, therefore requiring no actual repression of religion. Systematic criticism of the philosophical underpinnings of religion paralleled the upsurge of scientific discourse within industrial society. T.H. Huxley in 1869 coined the term "agnostic," a term subsequently adopted by such figures as Robert Ingersoll. Later, Bertrand Russell told the world Why I Am Not a Christian.
Many contemporary critics fault religion as being irrational. Some assert that dogmatic religions are in effect morally deficient, elevating to moral status ancient, arbitrary, and ill-informed rules—taboos on eating pork, for example, as well as dress codes and sexual practices—possibly designed for reasons of hygiene or even mere politics in a bygone era.
In North America and Western Europe the social fallout of the 9/11 attacks contributed in part to the appearance of numerous pro-secularist books, such as The God Delusion by Richard Dawkins, The End of Faith by Sam Harris, and God is not Great: How Religion Poisons Everything by Christopher Hitchens. This criticism is largely, but not entirely, focused on the monotheistic Abrahamic traditions.