From Wikipedia

Secular Believers

Secularism is the concept that government or other entities should exist separately from religion and/or religious beliefs.

In one sense, secularism may assert the right to be free from religious rule and teachings, and freedom from the government imposition of religion upon the people, within a state that is neutral on matters of belief. (See also Separation of church and state and Laïcité.) In another sense, it refers to the view that human activities and decisions, especially political ones, should be based on evidence and fact unbiased by religious influence. (See also public reason.)

Secularism draws its intellectual roots from Greek and Roman philosophers such as Marcus Aurelius and Epicurus, medieval Muslim polymaths such as Ibn Rushd, Enlightenment thinkers like Denis Diderot, Voltaire, John Locke, James Madison, Thomas Jefferson, and Thomas Paine, and modern freethinkers, agnostics and atheists such as Bertrand Russell and Robert Ingersoll.

The purposes and arguments in support of secularism vary widely. In European laicism, it has been argued that secularism is a movement toward modernization, and away from traditional religious values (also known as "secularisation"). This type of secularism, on a social or philosophical level, has often occurred while maintaining an official state church or other state support of religion. In the United States, some argue that state secularism has served to a greater extent to protect religion from governmental interference, while secularism on a social level is less prevalent. Within countries as well, differing political movements support secularism for varying reasons.