Let us define Monad first:
A Theosophical definition of Monad :
Monad
A spiritual entity which to us humans is indivisible; it is a divine-spiritual life-atom, but indivisible because its essential characteristic,
as we humans conceive it, is homogeneity; while that of the physical atom, above which our consciousness soars, is divisible, is a composite heterogeneous particle.
Monads are eternal, unitary, individual life-centers, conscious-ness-centers, deathless during any solar manvantara, therefore ageless, unborn, undying. Consequently, each one such - and their number is infinite - is the center of the All, for the divine or the All is THAT which has its center everywhere, and its circumference or limiting boundary nowhere.
Monads are spiritual-substantial entities, self-motivated, self-impelled, self-conscious, in infinitely varying
[COLOR=orange! important][COLOR=orange! important]degrees[/color][/color], the ultimate elements of the universe. These monads engender other monads as one seed will produce multitudes of other seeds; so up from each such monad springs a host of living entities in the course of illimitable time, each such monad being the fountainhead or parent, in which all others are involved, and from which they spring.
Every monad is a seed, wherein the sum total of powers appertaining to its divine origin are latent, that is to say unmanifested; and evolution consists in the growth and development of all these seeds or children monads, whereby the universal life expresses itself in innumerable beings.
As the monad descends into matter, or rather as its ray - one of other innumerable rays proceeding from it - is propelled into matter, it secretes from itself and then excretes on each one of the seven planes through which it passes, its various vehicles, all overshadowed by the self, the same self in you and in me, in plants and in animals, in fact in all that is and belongs to that hierarchy. This is the one self, the supreme self or paramatman of the hierarchy. It illumines and follows each individual monad and all the latter's hosts of rays - or children monads. Each such monad is a spiritual seed from the previous manvantara, which manifests as a monad in this manvantara; and this monad through its rays throws out from itself by secretion and then excretion all its vehicles. These vehicles are, first, the spiritual ego, the reflection or copy in miniature of the monad itself, but
individualized through the manvantaric evolution, "bearing" or "carrying" as a vehicle the monadic ray. The latter cannot directly contact the lower planes, because it is of the monadic essence itself, the latter
a still higher ray of the infinite Boundless composed of infinite multiplicity in unity. (
See also Individuality)