Speaking of her discovery, Mary Baker Eddy shares this:

"The divine hand led me into a new world of light and Life, a fresh universe—old to God, but new to His “little one.” It became evident that the divine Mind alone must answer, and be found as the Life, or Principle, of all being; and that one must acquaint himself with God, if he would be at peace. He must be ours practically, guiding our every thought and action; else we cannot understand the omnipresence of good sufficiently to demonstrate, even in part, the Science of the perfect Mind and divine healing.

I had learned that thought must be spiritualized, in order to apprehend Spirit. It must become honest, unselfish, and pure, in order to have the least understanding of God in divine Science. The first must become last. Our reliance upon material things must be transferred to a perception of and dependence on spiritual things. For Spirit to be supreme in demonstration, it must be supreme in our affections, and we must be clad with divine power. Purity, self-renunciation, faith, and understanding must reduce all things real to their own mental denomination, Mind, which divides, subdivides, increases, diminishes, constitutes, and sustains, according to the law of God."

—Mary Baker Eddy, Retrospection and Introspection, pp. 27–28