The Revelator, John, clearly discerned that all men would eventually be assured of the efficacy of divine Science. In the Bible we read (Rev. 3:9), "Behold, I will make them to come and worship before thy feet, and to know that I have loved thee."
Spiritual assurance comes from one's understanding of God and of spiritual man, the only man there is. The spiritual record of creation, as given in the first chapter of Genesis, forms the basis of Mary Baker Eddy's "scientific statement of being," which concludes (Science and Health with Key to the Scriptures, p. 468): "Spirit is God, and man is His image and likeness. Therefore man is not material; he is spiritual."
Spiritual assurance always attends the perception and acknowledgment of man's at-one-ment with the Father. Assurance of divine reality precludes any belief that man could ever deviate from his true being or that he could ever be outside the divine presence. It enables one to know that man is always the loved of Love.