Both philosophy and religion address the issue of God, though philosophy does not concern itself exclusively with God as religion does. Philosophy tends to concentrate more on the “ideas” in religion. Depending on the extent and power of religious ideas in the cultures in which they lived, philosophers have had different degrees of relation to theology. For example, when the Catholic Church was the dominant institution in Europe during the medieval period, philosophers such as Thomas Aquinas (c. 1225–1274) devoted most of their work to questions related to God.

Ancient Greek philosophers, who were later known as “pagans,” were less interested in religion, and by the eighteenth century Enlightenment, much of philosophy was secular. This secularization of philosophy was partly the result of David Hume’s (1711–1776) skeptical writings about both the practice of religion and the existence of God. Nineteenth and twentieth century philosophers developed the field as a form of secular inquiry that does not require religious commitment.