Deists believe in a supreme universal creator but do not believe that God is intimately involved in human affairs, either through miracles or revelations or other expressions of divine intervention. God's plan can be made plain by careful examination of the ways of the natural world.
Deism was popular in the 17th and 18th centuries and can be seen as an outgrowth of the Age of Enlightenment, which held that the application of human intelligence and ingenuity could solve most if not all of the problems facing societies. The Age of Enlightenment has thus been seen as a precursor to socialism and even communism in that it postulates that human beings can control all parts of their own environment. Deism is said to have influenced both Unitarianism and Universalism, religions that rejected many of the traditions of Western faith.
Deists believe that God created laws of nature and that to understand these laws is to see the face of God. The person considered to be most influential in Deism is Lord Herbert of Cherbury (d. 1648). He wrote a book, De Veritate that explained Deism and his viewpoints influenced such famous intellectuals abroad as Voltaire, in France. Thomas Jefferson was a famous American Deist who is said to have rejected the divinity of Jesus Christ, yet esteemed him as a great moral teacher. For such reasons, Deists were held in the past to be atheists of a sort, though they were not.
Because of its radical elements, Deists suffered from a certain stigmatism, especially during their heyday in the 1700s and 1800s. This is understandable, given that Deists were disdainful of "scripture," calling it a kind of "flim-flam." Deists were determined to know God by his works, his creations and to understand their relationship to God through much the same approach.
The first thing I shall insist upon is that if any doctrine of the New Testament be contrary to reason, we have no manner of idea of it. To say, for instance, that a ball is white and black at once is to say just nothing, for these colors are so incompatible in the same subject as to exclude all possibility of a real positive idea or conception. So to say as the papists that children dying before baptism are damned without pain signifies nothing at all. —John Toland, Christianity Not Mysterious or, a Treatise Shewing That There Is Nothing in the Gospel Contrary to Reason Nor above It (1696)
Despite their emphasis on logic when it came to understanding God, some Deists granted the possibility of a soul and therefore an afterlife. Benjamin Franklin, a notable Deist, is said to have believed in reincarnation or resurrection. Thomas Paine apparently took no position. He wrote in his Age of Reason: "I trouble not myself about the manner of future existence. I content myself with believing, even to positive conviction, that the power that gave me existence is able to continue it, in any form and manner he pleases, either with or without this body."
While Deism is seen as a fairly modern belief system, some of the hallmarks of Deism were evident long ago. Heraclitus is said to have conceived of God within a framework of extreme rationality and Plato spoke of god as craftsman. It is possible that Deism received its initial impulse during the Renaissance when the thoughts and writings of great Greek and Roman thinkers and artists were rediscovered and imitated. Deism may also have received a certain impetus from the study of ancient texts and the discovery that such texts had often been inaccurately transcribed or interpreted. This may have cast doubt on sacred texts.
Another influence that may have encouraged the growth of Deism was the gradual discovery of the non-European world by Western explorers. The subsequent enlightenment as regards other religions and philosophies likely also played a role in creating more skepticism about native religious beliefs. Finally, advances in science and medicine influenced the way people began to look at their belief structures.
Deism underwent a decline in the 1800s and by the 20th century it could be said that Deism was a far less influential belief system than it was in the 1700s when many of the most sophisticated thinkers of the age either claimed to be Deist or had sympathies for it.