In the 1908 edition of "Science and Health with Key to the Scriptures" Mary Baker Eddy added a paragraph at the end of the chapter, "Christian Science Practice," which she considered of sufficient importance to have it brought to the special attention of her followers through a notice in the Christian Science Sentinel, asking them to give it their daily consideration. (See The First Church of Christ, Scientist, and Miscellany, p. 237.) The paragraph reads (Science and Health, p. 442), "Christian Scientists, be a law to yourselves that mental malpractice cannot harm you either when asleep or when awake."
In this present hour, when a false psychology is being unscrupulously applied in an effort to influence the conclusions of people, both as classes and as masses, it is more than ever important for individuals to learn how to be a law to themselves, so that they will not blindly carry out the programs of trained propagandists or be caught in the net of some ambitious leader. Today there is need to cultivate an intelligent mental freedom. This includes the freedom to distinguish right from wrong, to discern between appeals to selfishness and fear and what God, infinite Mind, is proclaiming and revealing to individual consciousness, unmolested by verbal argument and unmoved by the silent pressure of multiplied human opinions.
It is plain that being a law to oneself is at the very basis of true self-government. It not only implies a freedom from belief in many minds, but also implies that one's thinking should have some stable and permanent foundation. Christian Science furnishes this true basis by revealing God as the divine Principle of man. This means that God, the one infinite and ever-present Mind, is the source of all real intelligence.