All matter as we know it through our senses--prakriti, as it is called in the Secret Doctrine to distinguish it from non-sensual matter--is the vibration of an universal Something, we do not know what, through these different octaves. The elementary substances (so-called) are one and the same thing--this Something--in different keys and chords of vibration; keys that run into one another, producing all sorts of beautiful harmonies. Taking any one of these elements, or any of their compounds, all we know of it is limited strictly to its changes during vibration through one octave. What happens when the vibration goes above or below the octave has not yet been treated hypothetically. While some elements are vibrating on higher and some on lower keys, we can consider them all as vibrating within one great octave, that octave of the universal Something which produces sensual matter, or prakriti. But matter is not confined, we know, to this great octave, although our sensual knowledge of it is strictly confined to it. How do we know it? Knowledge comes to us in two ways, and there are two kinds of knowledge. 1. That which comes through our senses, by observation and experience. This includes reasoning from relation. 2. That which comes through intuition--or, as some writers inaccurately say, "through the formal laws of thought." All the observation and experience of the rising and the setting of the sun for a thousand centuries could only have confirmed the first natural belief that it revolved daily around the earth; nor by joining this experience with other experiences could any deduction have come from our reason that would have opposed it. Not our reason but our intuition said that the sun stood still and the earth revolved daily. The oldest books in existence tell us that this axial revolution of the earth was not only known in the very dawn of time but that it has been known to every race (except our own of European savages) from before the time thought was first transmitted by writing. Ask the ablest living geographer or physicist to prove to you that the earth revolves daily and he will reply that it would be the job of his life. It can be done at great expense and great labor, but that is because we know the answer and can invent a way of showing it, not because there are any observations from which a deduction would naturally follow.