Isaac Newton (4 January 1643 – 31 March 1727) was considered an insightful and erudite theologian by his Protestant contemporaries. He wrote many works that would now be classified as occult studies, and he wrote religious tracts that dealt with the literal interpretation of the Bible. He kept his heretical beliefs private.

Newton's conception of the physical world provided a model of the natural world that would reinforce stability and harmony in the civic world. Newton saw a monotheistic God as the masterful creator whose existence could not be denied in the face of the grandeur of all creation. Born into an Anglican family, he became a devout but heterodox Protestant Christian. By his thirties Newton held a Christian faith that, had it been made public, would not have been considered orthodox by mainstream Christians. Many scholars now consider him a Nontrinitarian Arian.

He may have been influenced by Socinian christology.

Newton was born into an Anglican family three months after the death of his father, a prosperous farmer also named Isaac Newton. When Newton was three, his mother married the rector of the neighbouring parish of North Witham and went to live with her new husband, the Reverend Barnabas Smith, leaving her son in the care of his maternal grandmother, Margery Ayscough. Isaac apparently hated his step-father, and had nothing to do with Smith during his childhood. His maternal uncle, the rector serving the parish of Burton Coggles, was involved to some extent in the care of Isaac.

In 1667, Newton became a Fellow of Trinity College, Cambridge, making necessary his commitment to taking Holy Orders within seven years of completing his MA, which he did the following year. He was also required to take a vow of celibacy and recognize the Thirty-Nine Articles of the Church of England. Newton considered ceasing his studies prior to completion to avoid the ordination made necessary by law of King Charles II. He was eventually successful in avoiding the statute, assisted in this by the efforts of Isaac Barrow, as in 1676 the then Secretary of State for the Northern Department, Joseph Williamson, changed the relevant statute of Trinity College to provide dispensation from this duty. Newton then embarked on an investigative study of the early history of the Church, which developed, during the 1680s, into inquiries about the origins of religion. At around the same time, he developed a scientific view on motion and matter. Of Philosophiæ Naturalis Principia Mathematica he stated:

When I wrote my treatise about our Systeme I had an eye upon such Principles as might work with considering men for the beliefe of a Deity and nothing can rejoyce me more than to find it useful for that purpose.

According to most scholars, Newton was Arian, not holding to Trinitarianism. Scholars have generally concluded that Newton's heretical beliefs were self-taught, but he may have been influenced by then-current heretical writings; controversies over unitarianism were raging at the time.

As well as rejecting the Trinity, Newton's studies led him to reject belief in the immortal soul. Despite his unorthodox beliefs, Sir Isaac Newton affirmed infant baptism, in keeping with his Anglican upbringing, writing, "The Declaration by imposition of hands is a Jewish ceremony. We call it confirmation, meaning a confirmation of what was done by the Godfathers in baptizing the Infant."