Tennent was an Irish-born American Presbyterian clergyman, son and brother of three other Presbyterian clergymen. His father, William Tennent, emigrated to America in 1718, and was the founder of a theological school at Warminster, Pennsylvania called, because of the way it was housed, the Log College. Log College is regarded as the precursor to Princeton University. Gilbert was one of the leaders of the Great Awakening of religious feeling in Colonial America, along with Jonathan Edwards and George Whitefield. His most famous sermon, "On the Danger of an Unconverted Ministry" compared anti-revivalistic ministers to the Pharisees described in the gospels. For notices of Gilbert and other prominent members of the Tennent family, consult W. B. Sprague, Annals of the American Pulpit, volume iv (New York, 1858).