Hobbes, in his philosophy of natural law, believed that absolutist rulers emerged according to the baser instincts of humans, specifically their fear of death and their need for power. In his philosophy, there could be no social order without the ceding of power to a single individual who would use power to restrain the violent and anti-social tendencies of the people.
To those who believed the absolute ruler was chosen by God, rebellion against the monarch was tantamount to rebellion against God. Hence, rule was considered "absolute," in that the ruler could not be challenged.
Later absolutist rulers sometimes tried to rule according to Enlightenment principles, and so are called enlightened absolutists. They attempted to allow their subjects to live more freely in their day-to-day lives, while still maintaining the autocratic monarchy.
Absolutism, as a term, did not appear until the 19th century, when the traditional "age of absolutism" had passed.
Some historians see the Absolutist Monarchs as a direct consequence of the centralization of the state under the New Monarchs.