The terms Old Lights and New Lights (among others) are used in Christian circles to distinguish between two groups who were initially the same, but have come to a disagreement. These terms have been applied in a wide variety of ways, and the meaning must be determined from context. Typically, if a denomination is changing, and some refuse to change, and the denomination splits, those who did not change are referred to as the "Old Lights", and the ones who changed are referred to as the "New Lights".

The terms were first used during the First Great Awakening, which spread through the British North American colonies in the middle of the 18th century.^{[citation needed]} In A Faithful Narrative of the Surprising Work of God (1737), Jonathan Edwards, a leader in the Awakening, describes his congregants vivid experiences with grace as causing a "new light" in their perpective on sin and atonement. Old Lights and New Lights generally referred to Congregationalists and Baptists in New England who took different positions on the Awakening than the traditional branches of their denominations. New Lights embraced the revivals that spread through the colonies, while Old Lights were suspicious of the revivals (and their seeming threat to authority). Historian Richard Bushman credits the division between Old Lights and New Lights for the creation of political factionalism in Connecticut in the mid-eighteenth century. Often "many "new light" Congregationalists who had been converted under the preaching of George Whitefield left that connection to become "new light" Baptists when they found no evidence of infant baptism in the apostolic church, they left. When told of this development, Whitefield famously quipped that he was glad to hear about the fervent faith of his followers but regretted that "so many of his chickens had become ducks." Then they went off.New Side" and those opposed to the revivals called "Old Side."