The Enlightenment of the 17th and 18th centuries developed as a product of the ability to reason examined by ancient Greek philosophers such as Aristotle and Plato. As Christianity grew in popularity in the Greco-Roman world, Christian theologians felt the need to meld Christian thought with the earlier ancient Greek philosophers. Through this need, Christian philosophers of the Middle Ages developed a school of thought called Scholasticism in which ancient Greek dialectical reasoning was employed to develop arguments, counterarguments, conclusions, and to answer questions or fix contradictions. Scholasticism is considered our basis for logical reasoning.
However, soon, Christianity began being attacked in the age of the Renaissance by humanism and the Protestant Reformation. Since humanism places emphasis on human experiences, humanism gave birth to experimental scientists like Francis Bacon, Nicolaus Copernicus, and Galileo and to mathematicians like Rene Descartes and Isaac Newton. Due to their methods of reasoning, reasoning began to be even more important than Christianity itself, leading to the birth of Deism. Deists conflicted with Christians in that they rejected all religious truths except for the existence of one God. However, they saw God as an architect of the world, who, beyond being the architect, is no longer involved in humanity in terms of revelations. Many Deists are also celebrated Enlightenment thinkers, such as Thomas Hobbes, Thomas Jefferson.
In contrast to the Enlightenment, the Great Awakening, which also emerged in the 18th century, revived all of the theology rejected by Deists. The Great Awakening arose as a product of all the various Protestant churches in the American colonies, especially Calvinism. Great Awakening ministers preached of God's grace, spiritual rebirth through Jesus Christ, and warned sinners of the terrors of God's wrath. Jonathan Edwards, one of the most famous Great Awakening apologists also revived the idea of revelation the Deists of the Enlightenment had rejected. He attempted to explain the works of the Holy Spirit in helping believers determine right from wrong and taught that salvation was earned through faith alone, not through works.
Hence, Enlightenment thinkers and Great Awakening theologians taught very opposing beliefs. Whereas Enlightenment thinkers emphasized reason, Great Awakening theologians emphasized faith. Whereas Enlightenment Deists rejected the notion of salvation through Jesus Christ and continuous revelations from God, Great Awakening theologians revived religious ideas of salvation and taught individuals could experience daily revelations through the Holy Spirit.