Science and Health with Key to the Scriptures first appeared in 1875, and Eddy revised it for the rest of her life, through hundreds of printings, tightening the argument and reordering the chapters. Its claim is total: God is Mind and is the only reality, matter has no existence of its own, and sickness, sin and death are therefore errors of mortal belief rather than facts to be treated. Healing is accomplished by seeing through the error, and the practice of doing so, she held, was a demonstrable science that anyone could learn.
The institutional design is as distinctive as the doctrine and rather more original. In a Church of Christ, Scientist there is no sermon and no minister. Two lay readers, elected for a term, read a lesson made up of passages from the Bible and from Science and Health, in a sequence set centrally, and that is the whole service. Eddy abolished preaching deliberately, on the ground that a personality in a pulpit would come between the congregation and the two books.
She fixed the arrangement in a Manual of The Mother Church, a short book of by-laws that governs the denomination still, and which contains provisions that can be enacted only with her consent, so that the structure she left cannot readily be altered. The result is one of the most tightly specified religious institutions ever created by a single person.