In other words, they have to learn with that absolute certainty that comes not by theory, but by practical experience, that in their astral bodies none of these elements can by any possibility be hurtful to them--that none can oppose any obstacle in the way of the work which they have to do. In this physical body we are fully convinced that fire will burn us, that water will drown us, that the solid rock forms an impassable barrier to our progress, that we cannot with safety launch ourselves unsupported into the ambient air. So deeply is this conviction engrained in us that it costs most men a good deal of effort to overcome the instinctive action which follows from it, and to realize that in the astral body the densest rock offers no impediment to their freedom of motion, that they may leap with impunity from the highest cliff, and plunge with the most absolute confidence into the heart of the raging volcano or the deepest abysses of the fathomless ocean. Yet until a man _knows_ this--knows it sufficiently to act upon his knowledge instinctively and confidently--he is comparatively useless for astral work, since in emergencies that are constantly arising he would be perpetually paralyzed by imaginary disabilities. So he has to go through his tests, and through many another strange experience--to meet face to face with calm courage the most terrifying apparitions amid the most loathsome surroundings--to show in fact that his nerve may be thoroughly trusted under any and all of the varied groups of circumstances in which he may at any moment find himself. Further, we need control of mind and of desire; of mind, because without the power of concentration it would be impossible to do good work amid all the distracting currents of the astral plane; of desire, because in that strange world to desire is very often to have, and unless this part of our nature were well controlled we might perchance find ourselves face to face with creations of our own of which we should be heartily ashamed. 3. _Calmness._ This is another most important point--the absence of all worry and depression. Much of the work consists in soothing those who are disturbed, and cheering those who are in sorrow; and how can a helper do that work if his own aura is vibrating with constant fuss and worry, or grey with the deadly gloom that comes from perpetual depression? Nothing is more hopelessly fatal to occult progress or usefulness than our nineteenth-century habit of ceaselessly worrying over trifles--of eternally making mountains out of molehills. Many of us simply spend our lives in magnifying the most absurd trivialities--in solemnly and elaborately going to work to make ourselves miserable about nothing.