Newton's interest in theological matters ran broadly and deeply, extending beyond the conviction, expressed in such scientific works as his Principia and his Opticks, regarding God's role as creator and maintainer of the universe. In The Chronology of Ancient Kingdoms Amended (1728) and Observations upon the Prophecies of Daniel and the Apocalypse of St. John (1733), as well as in numerous unpublished manuscripts, Newton reveals an interest in wide-ranging aspects of biblical study. In these works he contemplates the historical accuracy of the Bible, the way in which biblical prophecies may be understood and proved, and the corruptions he believed were deliberately incorporated into the Bible in support of the doctrine of the Trinity, which Newton believed to be false. For a time, many critics ignored or disparaged Newton's theological interests; modern scholars, however, have investigated the nature and implications of his beliefs, exploring the relationship of his theological views to his scientific studies.
The only one of his theological works that Newton authorized to have published was The Chronology of Ancient Kingdoms Amended, which he prepared for press prior to his death in 1727. Observations upon the Prophecies of Daniel and the Apocalypse of St. John was arranged and published after Newton's death by his nephew. In the Chronology Newton uses astronomical discoveries to construct a biblical chronology based upon the positions of the stars as described in Scripture and other ancient writings. By means of this astronomical evidence, Newton argues that the Bible is accurate as history and that it is the oldest historical record available. In Observations Newton focuses on the composition of the books of the Bible. Through his historical analysis, he contends that Moses did not write all parts of the Pentateuch, the first five books of the Bible. Newton also emphasizes in Observations that biblical prophesies have been fulfilled in history and will continue to be fulfilled; yet he does not advocate the study of such prophesies for the purpose of predicting the future. Newton's analysis of the Bible also reveals his belief that individuals such as St. Athanasius purposely corrupted the New Testament in order to support the doctrine of the Trinity, insisting that it cannot be proved from Scripture that Jesus was co-substantial with God.
Many critics have looked to Newton's published and unpublished theological writings in order to flesh out the nature of his beliefs. Filled with extensive and detailed historical and Biblical scholarship, Newton's Observations has been the focus of study for a number of critics. Leonard Trengove outlines the scope and content of this work, examining Newton's disbelief in the Trinity and the biblical basis for this departure from the accepted tenets of the Church of England. Richard H. Popkin similarly examines Observations as well as various unpublished manuscripts in his survey of Newton's conclusions regarding the composition of the Pentateuch as well as the commentary of Newton's contemporaries who agreed with or took issue with his findings. Additionally, Popkin reviews the content of the Chronology, stressing that Newton, having analyzed biblical records, believed that God had outlined a plan for human history and natural history alike. Among other investigations of Newton's manuscripts is that of J. E. McGuire and P. M. Rattansi, which analyzesthe drafts of a Scholia to Propositions IV through IX of Book III of Newton's Principia. According to the critics, these drafts indicate Newton's conviction that God had revealed knowledge to the ancients, and that he, Newton, was rediscovering those truths. In his study of Newton's unpublished writings, Frank Manuel demonstrates how many of these materials indicate that Newton's religion, throughout his life, was one of "obedience to commandments in which the mercies of Christ the Redeemer played a recessive role."
Another area of critical investigation has been that of the relationship between Newton's theological interests and his scientific achievements. James E. Force points out that, while Newton's references to God in his scientific works indicate that his theology exerted some degree of influence on his scientific thinking, many critics still tend to divorce Newton's scientific interests from his theological views. Taking the reverse approach, William H. Austin attempts to ascertain the influence of Newton's science on his theology. Citing Newton's maxim that "religion and Philosophy are to be preserved distinct," Austin concludes that there is little evidence in Newton's theological writings to suggest the influence of his scientific ideas. However, the critic notes, Newton appears to have held to this maxim inconsistently, and perhaps allowed that science had some influence on his theology, possibly to avoid public controversy. Force disagrees, maintaining that Newton's conception of a "God of Dominion" integrates his scientific, theological, and political interests. In his analysis of the unity of Newton's thought, Force states that "Newton's theology, not just his religion, influences his science every bit as much as his science influences the rigorous textual scholarship of his theology."