The four truths written on the first page of "Light on the Path," refer to the trial initiation of the would-be occultist. Until he has passed it, he cannot even reach to the latch of the gate which admits to knowledge. Knowledge is man's greatest inheritance; why, then, should he not attempt to reach it by every possible road? The laboratory is not the only ground for experiment; _science_, we must remember, is derived from _sciens_, present participle of _scire_, "to know,"--its origin is similar to that of the word "discern," to "ken." Science does not therefore deal only with matter, no, not even its subtlest and obscurest forms. Such an idea is born merely of the idle spirit of the age. Science is a word which covers all forms of knowledge. It is exceedingly interesting to hear what chemists discover, and to see them finding their way through the densities of matter to its finer forms; but there are other kinds of knowledge than this, and it is not every one who restricts his (strictly scientific) desire for knowledge to experiments which are capable of being tested by the physical senses. Everyone who is not a dullard, or a man stupefied by some predominant vice, has guessed or even perhaps discovered with some certainty, that there are subtle senses lying within the physical senses. There is nothing at all extraordinary in this; if we took the trouble to call Nature into the witness box we should find that everything which is perceptible to the ordinary sight, has something even more important than itself hidden within it; the microscope has opened a world to us, but within those encasements which the microscope reveals, lies a mystery which no machinery can probe. The whole world is animated and lit, down to its most material shapes, by a world within it. This inner world is called Astral by some people, and it is as good a word as any other, though it merely means starry; but the stars, as Locke pointed out, are luminous bodies which give light of themselves. This quality is characteristic of the life which lies within matter; for those who see it, need no lamp to see it by. The word star, moreover, is derived from the Anglo-Saxon "stir-an," to steer, to stir, to move, and undeniably it is the inner life which is master of the outer, just as a man's brain guides the movements of his lips. So that although Astral is no very excellent word in itself, I am content to use it for my present purpose.