Having understood this truth, mystics have been able to teach that the religion of all religions is the knowledge of self, for the knowledge of self brings the knowledge of life. This life-current which runs through the center of man's being, attaching mind to body and to all other planes of existence as well, it is this that is all important. It passes from man's innermost being out to the body, which is the instrument whereby man is able to experience life on the surface. When he has knowledge of this a man begins to realize, "I am not as small as I had thought, not as weak as I had thought; I am much stronger on other planes. I can live much longer than I could on the physical plane. I can see myself on all the different planes by means of that inner knowledge of the breath."