Enlightenment Deism.  
Aspects of Deism in Enlightenment philosophy.  
Enlightenment Deism consisted of two philosophical assertions: (1) reason, along with features of the natural world, is a valid source of religious knowledge, and (2) revelation is not a valid source of religious knowledge. Different Deist philosophers expanded on these two assertions to create what Leslie Stephen later termed the "constructive" and "critical" aspects of Deism.  "Constructive" assertions—assertions that deist writers felt were justified by appeals to reason and features of the natural world (or perhaps were intuitively obvious or common notions)—included:  
- God exists and created the universe.  
- God gave humans the ability to reason.  
"Critical" assertions—assertions that followed from the denial of revelation as a valid source of religious knowledge—were much more numerous, and included:  
- Rejection of all books (including the Quran and the Bible) that claimed to contain divine revelation. 
- Rejection of the incomprehensible notion of the Trinity and other religious "mysteries".  
- Rejection of reports of miracles, prophecies, etc.  
The origins of religion.  
A central premise of Deism was that the organized religions of their day were corruptions of an original religion that was pure, natural, simple, and rational. Humanity lost this original religion when it was subsequently corrupted by priests who manipulated it for personal gain and for the class interests of the priesthood, and encrusted it with superstitions and "mysteries"—irrational theological doctrines. Deists referred to this manipulation of religious doctrine as "priestcraft", a derogatory term. For Deists, this corruption of natural religion was designed to keep laypeople baffled by "mysteries" and dependent on the priesthood for information about the requirements for salvation. This gave the priesthood a great deal of power, which the Deists believed the priesthood worked to maintain and increase. Deists saw it as their mission to strip away "priestcraft" and "mysteries". Matthew Tindal, perhaps the most prominent Deist writer in early modern Europe, claimed that this was the proper, original role of the Christian Church.  
One implication of this premise was that current-day primitive societies, or societies that existed in the distant past, should have religious beliefs less infused with superstitions and closer to those of natural theology. This position became less and less plausible as Enlightenment philosophers such as David Hume began studying the natural history of religion and suggested that the origin of religion was not in reason but in emotions, such as the fear of the unknown.  
Immortality of the soul.  
Different Deists had different beliefs about the immortality of the soul, about the existence of Hell and damnation to punish the wicked, and the existence of Heaven to reward the virtuous. Anthony Collins, Bolingbroke, Thomas Chubb, and Peter Annet were materialists and either denied or doubted the immortality of the soul. Benjamin Franklin believed in reincarnation or resurrection. Lord Herbert of Cherbury and William Wollaston held that souls exist, survive death, and in the afterlife are rewarded or punished by God for their behavior in life. Thomas Paine believed in the "probability" of the immortality of the soul.  
Miracles and divine providence.  
The most natural position for Deists was to reject all forms of supernaturalism, including the miracle stories in the Bible. The problem was that the rejection of miracles also seemed to entail the rejection of divine providence (that is, God taking a hand in human affairs), something that many Deists were inclined to accept. Those who believed in a watch-maker God rejected the possibility of miracles and divine providence. They believed that God, after establishing natural laws and setting the cosmos in motion, stepped away. He did not need to keep tinkering with his creation, and the suggestion that he did was insulting. Others, however, firmly believed in divine providence, and so, were reluctantly forced to accept at least the possibility of miracles. God was, after all, all-powerful and could do whatever he wanted including temporarily suspending his own natural laws.  
Freedom and necessity.  
Enlightenment philosophers under the influence of Newtonian science tended to view the universe as a vast machine, created and set in motion by a creator being, that continues to operate according to natural law without any divine intervention. This view naturally led to what was then called "necessitarianism" (the modern term is "determinism"): the view that everything in the universe—including human behavior—is completely, causally determined by antecedent circumstances and natural law. (See, for example, La Mettrie's L'Homme machine.) As a consequence, debates about freedom versus "necessity" were a regular feature of Enlightenment religious and philosophical discussions. Reflecting the intellectual climate of the time, there were differences among Deists about freedom and determinism. Some, such as Anthony Collins, were actually necessitarians.  

David Hume,  
Views differ on whether David Hume was a Deist, an atheist, or something else. Like the Deists, Hume rejected revelation, and his famous essay On Miracles provided a powerful argument against belief in miracles. On the other hand, he did not believe that an appeal to Reason could provide any justification for religion. In the essay Natural History of Religion (1757), he contended that polytheism, not monotheism, was "the first and most ancient religion of mankind" and that the psychological basis of religion is not reason, but fear of the unknown. In Waring's words:  
The clear reasonableness of natural religion disappeared before a semi-historical look at what can be known about uncivilized man— "a barbarous, necessitous animal," as Hume termed him. Natural religion, if by that term one means the actual religious beliefs and practices of uncivilized peoples, was seen to be a fabric of superstitions. Primitive man was no unspoiled philosopher, clearly seeing the truth of one God. And the history of religion was not, as the deists had implied, retrograde; the widespread phenomenon of superstition was caused less by priestly malice than by man's unreason as he confronted his experience. 


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