The modern historical era of liberal theology basically encompass four distinct phases of change. The Enlightenment phase extends from the seventeenth century to approximately the middle or late eighteenth century. It is followed by the Romantic phase which is prominent until the mid-nineteenth century when it fades and then rise in the form of Modernism. The final, or perhaps more appropriately, the present phase of liberalism (often referred to as Neo-liberalism) began to surface during the twentieth century.

Even though research indicate liberal thought in actuality antedates the aforementioned phases, for purposes of brevity and clarity, this article shall focus on liberal thought as it developed from the age of the enlightenment to the present.

The age of Enlightenment was characterized by the triumph of reason in religion and the evanescence of the doctrine of revelation. Rationalism stressed the a priori ability of human reason to know truth; what could be known could only be known through reason and what could not be known by reason was not truth. Revelation and authority therefore, were not only dismissed as irrelevant but totally unnecessary as well. The chief exponents of rationalism were Descartes, Spinoza and Leibniz.

Rationalism gained its first systematic philosophical formulation in the works of Descartes. He applied the mathematical method to human reasoning and argued for a priori ideas and principles. He attempted to prove God