Christian Science is a cult that was founded by Mary Baker Eddy in the 19th century, built upon the premise in her 1875 book, Science and Health, that illness doesn’t technically exist and can be dispelled by prayer. Christian Science came on the tail end of the Restorationist Movement.
Eddy founded the Church of Christ, Scientist in 1879 the first congregation developed in Boston in 1894. Peaking in the 1930s with over a quarter-million followers, the religion now has little more than one hundred thousand.
The chief distinctive of Christian Science is denying members major medical care (although minor medical care like dentistry and optometry are often allowed), due to a belief that physical reality doesn’t exist, and all ailments can be overcome by prayer.
However, denying medical assistance isn’t what makes Christian Science a sub-Christian sect (it is foolish, but not heretical). Essentially, Christian Science is almost entirely devoid of anything inherently Biblical. Concepts like grace, propitiation, the atonement, imputed righteousness or depravity are altogether absent from Christian Science teaching. Also absent from Christian Science is any focus on the incarnation of Christ, his death, burial or resurrection. Christian Science teaches panentheism and denies Original Sin.