Historical Context for Dialogues Concerning Natural Religion
Hume was born into the period of Enlightenment or the Age of Reason, a time when many writers were using the faculty of rational thought to investigate religion, politics, and social and moral matters. He was also, however, born in Britain, which had not yet become as freethinking about religious matters as the continent. Nearly all of his thought can be seen as molded by these two historical forces: the intellectual movement which encouraged him to push ideas to their logical limit, and the religious culture that warned him not to push too far.
Hume was an Enlightenment philosopher par excellence. In questions of metaphysics, epistemology, ethics, and religion he did not hesitate to disregard received wisdom. In the Treatise Concerning Human Nature he rocked the foundations of thousands of years of epistemology and common sense by showing convincingly that there is no justification for our judgments concerning cause and effect: when we see one ball hit another and subsequently see the second ball moving, for instance, we have no rational basis on which to claim that the first ball caused the second ball to move. Rather, we expect the second ball to move when hit by the first out of habit (that is, because we've seen similar things happen many times in the past and then assume that they will happen the same way again). Hume argued even though we have no rational reason to expect the movement of the second ball, we should continue to do so because such beliefs are natural and necessary for our survival. Similarly, Hume argued that we have no rational basis for our belief in a benevolent creator.
While Hume's radically skeptical epistemological claims received no notice during his lifetime (until Kant stumbled on them during the following century and "awoke from his dogmatic slumber") his skeptical religious claims were not as easily ignored. Though theological debates raged in England between the more rational deists and the Orthodox theists, it was unacceptable at that time to deny the existence of God. Hume, therefore, had to tiptoe around his true opinions. Even in the posthumously published Dialogues Concerning Natural Religion Hume takes great care to submerge his own opinion underneath layers of literary artifice: the work is written as a dialogue with the author's mouthpiece left unidentified.