Some of these old philosophers taught that the whole universe quiets down for a period; others maintained that this quieting down applies only to systems. That is to say, that while our system here, this solar system, will quiet down and go back into that undifferentiated state, there are millions of other systems going the other way. I should rather follow the second opinion, that this quieting down is not simultaneous over the whole universe, but that in different parts different things are going on. But the principle remains the same, that all that we see, that Nature herself is progressing in successive rises and falls. The one stage, going back to the balance, to the perfect equilibrium, is called the end of a cycle. The whole _Kalpa_, the evolution and the involution, has been compared by theistic writers in India to the inbreathing and outbreathing of God; God, as it were, breathes out the universe, and it returns into Him again. When it quiets down, what becomes of the universe? It still exists, only in finer form, as it is called in Sanskrit, in the “causal state” (_Kârana Sarira_). Causation, time and space are still there, only they are potential. This return to an undifferentiated condition constitutes involution. Involution and evolution are eternally going on, so that when we speak of a beginning, we refer only to the beginning of a cycle. The most extraneous part of the universe is what in modern times we call gross matter. The ancient Hindus called it the _Bhutas_, the external elements. There is one element which according to them is eternal; every other element is produced out of this one, and this eternal element is called _Âkâsa_. It is somewhat similar to the modern idea of ether, though not exactly the same. This is the primal element out of which everything proceeds, and along with this element there was something called _Prâna_: we shall see what it is as we go on. This _prâna_ and this _âkâsa_ eternally exist, and they combine and recombine and form all manifestation. Then at the end of the cycle everything subsides and goes back to the unmanifested form of _âkâsa_ and _prâna_. There is in the Rig Veda, the oldest scriptures in existence, a beautiful passage describing creation, and it is most poetical--“When there was neither ought nor nought, when darkness was rolling over darkness, what existed?” and the answer is given, “It (the Eternal One) then existed without motion.” _Prâna_ and _âkâsa_ were latent in that Eternal One, but there was no phenomenal manifestation. This state is called _Avyaktam_, which literally means “without vibration,” or unmanifested. At the beginning of a new cycle of evolution, this _avyaktam_ begins to vibrate and blow after blow is given by _prâna_ to the _âkâsa_. This causes condensation and gradually, through the forces of attraction and repulsion, atoms are formed. These in turn condense into molecules and finally into the different elements of Nature.