Life on the mental plane is more active than on the astral, and form is more plastic. The spirit-matter of that plane is more highly vitalized and finer than any grade of matter in the astral world. The ultimate atom of astral matter has innumerable aggregations of the coarsest mental matter for its encircling sphere-world, so that the disintegration of the astral atom yields a mass of mental matter of the coarsest kinds.
Under these circumstances it will be understood that the play of the life-forces on this plane will be enormously increased in activity, there being so much less mass to be moved by them. The matter is in constant, ceaseless motion, taking form under every thrill of life, and adapting itself without hesitation to every changing motion. “Mind-stuff,” as it has been called, makes astral spirit-matter seem clumsy, heavy, and lustreless, although compared with the physical spirit-matter it is so fairy-light and luminous. But the law of analogy holds good, and gives us a clue to guide us through this super-astral region, the region that is our birthplace and our home, although, imprisoned in a foreign land, we know it not, and gaze at descriptions of it with the eyes of aliens.
Once again here, as on the two lower planes, the subdivisions of the spirit-matter of the plane are seven in number. Once again, these varieties enter into countless combinations, of every variety of complexity, yielding the solids, liquids, gases and ethers of the mental plane. The word ‘‘solid” seems indeed absurd, when speaking of even the most substantial forms of mind-stuff; yet as they are dense in comparison with other will appear more plainly a little further on.
The distinction may perhaps be best expressed by saying that in the lower four subdivisions the vibrations of consciousness give rise to forms, to images or pictures, and every thought appears as a living shape; whereas in the higher three, consciousness, though still, of course, setting up vibrations, seems rather to send them out as a mighty stream of living energy which does not body itself into distinct images while it remains in this higher region, but which sets up a variety of forms all linked by some common condition, when it rushes into the lower worlds.
The nearest analogy that I can find for the conception I am trying to express is that of abstract and concrete thoughts; an abstract idea of a triangle has no form, but connotes any figure contained within three right lines, the angles of which make two right angles; such an idea, with conditions but without shape, thrown into the lower world, may give birth to a vast variety of figures, right-angled, isosceles, scalene, of any colour and size, but all fulfilling the conditions—concrete triangles, each one with a definite shape of its own.
The impossibility of giving in words a lucid exposition of the difference in the action of consciousness in the two regions is due to the fact that words are the symbols of images and belong to the workings of the lower mind in the brain, and are based wholly upon those workings; while the “formless” region belongs to the Pure Reason, which never works within the narrow limits of language.
***From Annie Besant – The Ancient Wisdom