It is necessary to understand something about that consciousness which is your Self, and about the matter which is the envelope of consciousness, but which the Self so often identifies with himself.

The great characteristic of consciousness is change, with a foundation of certainty that it is. The consciousness of existence never changes, but beyond this all is change, and only by the changes does consciousness become Self-consciousness.

Consciousness is an everchanging thing, circling round one idea that never changes--Self-existence. The consciousness itself is not changed by any change of position or place. It only changes its states within itself.

In matter, every change of state is brought about by change of place. A change of consciousness is a change of a state; a change of matter is a change of place. Moreover, every change of state in consciousness is related to vibrations of matter in its vehicle.

When matter is examined, we find three fundamental qualities--rhythm, mobility, stability--sattva, rajas, tamas.
Sattva is rhythm, vibration. It is more than; rajas, or mobility.

It is a regulated movement, a swinging from one side to the other over a definite distance, a length of wave, a vibration.

The question is often put: "How can things in such different categories, as matter and Spirit, affect each other? Can we bridge that great gulf which some say can never be crossed?"

Yes, the Indian has crossed it, or rather, has shown that there is no gulf. To the Indian, matter and Spirit are not only the two phases of the One, but, by a subtle analysis of the relation between consciousness and matter, he sees that in every universe the LOGOS imposes upon matter a certain definite relation of rhythms, every vibration of matter corresponding to a change in consciousness.

There is no change in consciousness, however subtle, that has not appropriated to it a vibration in matter;
there is no vibration in matter, however swift or delicate, which has not correlated to it a certain change in consciousness. That is the first great work of the LOGOS, which the Hindu scriptures trace out in the building of the atom, the Tanmatra, " the measure of That," the measure of consciousness.

He who is consciousness imposes on his material the answer to every change in consciousness, and that is an infinite number of vibrations. So that between the Self and his sheaths there is this invariable relation: the change in consciousness and the vibration of matter, and vice versa. That makes it possible for the Self to know the Not-Self.

These correspondences are utilised in Raja Yoga and Hatha Yoga, the Kingly Yoga and the Yoga of Resolve. The Raja Yoga seeks to control the changes in consciousness, and by this control to rule the material vehicles. The Hatha Yoga seeks to control the vibrations of matter, and by this control to evoke the desired changes in consciousness.

The weak point in Hatha Yoga is that action on this line cannot reach beyond the astral plane, and the great strain imposed on the comparatively intractable matter of the physical plane sometimes leads to atrophy of the
very organs, the activity of which is necessary for effecting the changes in consciousness that would be useful.

The Hatha Yogi gains control over the bodily organs with which the waking consciousness no longer concerns itself, having relinquished them to its lower part, the " subconsciousness',

This is often useful as regards the prevention of disease, but serves no higher purpose. When he begins to work on the brain centres connected with ordinary consciousness, and still more when he touches those connected
with the super-consciousness, he enters a dangerous region, and is more likely to paralyse than to evolve.

That relation alone it is which makes matter cognizable; the change in the thinker is answered by a change outside, and his answer to it and the change in it that he makes by his. answer re-arrange again the matter of the body which is his envelope.

Hence the rhythmic changes in matter are rightly called its cognizability. Matter may be known by consciousness, because of this unchanging relation between the two sides of the manifest LOGOS who is one, and the Self becomes aware of changes within himself, and thus of those of the external words to which those changes are related.