Biblical criticism, in particular higher criticism, covers a variety of methods used since the Enlightenment in the early 18th century as scholars began to apply to biblical documents the same methods and perspectives which had already been applied to other literary and philosophical texts. It is an umbrella term covering various techniques used mainly by mainline and liberal Christian theologians to study the meaning of biblical passages. It uses general historical principles, and is based primarily on reason rather than revelation or faith. There are four primary types of biblical criticism: