It is fair to ask whether the assurance of the presence of God enjoyed by many Christians in all ages, according to their testimony, is immediate or inferred knowledge, and whether it should be called knowledge or faith. The answer of the mystic might be that there is a "felt indubitable certainty of experience" which is not dependent on the solution of epistemological problems. Otherwise we could not be sure of our own existence or of that of our fellows until we had specialized in the theory of knowledge and solved the problem, which has haunted modern philosophy, of the knowledge of other selves. If it be objected again that a subjective experience cannot ground an inference to an objective, and much less to a supernatural, cause,[144] it may be said that the experience itself, if correctly reported, is supernatural in character. Whether it be Paul's "peace that passes understanding," or Peter's "joy unspeakable and full of glory," or Edwards' "inward sweet delight in God and divine things," or a modern scientist's consciousness of the presence of God, said to be "as strong and real to me as that of any bodily presence,"[145] it is of such a character that no other inference than that to a supernatural cause can properly be drawn. The mystical argument is not based like the other arguments of natural theology upon the regular course of things, but upon what claims to be a new supernatural experience, a new life with new capacities and powers, and new emotions and insights. 144: See Höffding: "Philosophy of Religion," p. 99. 145: "A Scientist's Confession of Faith," by E. L. Gregory, 1898, p.21.