The Monad: One and Many
'Monad' literally means 'unit'. In its broadest sense, it can therefore refer to any natural system or entity, any unitary individual -- from the vastest solar system to the tiniest atom. In general, every entity, on any plane, has within it a nucleus, a 'control centre' or 'nerve centre', of more highly developed energy-substance belonging to that plane, and this nucleus, too, can be called a monad. The term is commonly used in a still more restricted sense to refer only to the highest, spiritual portion of any entity's multi-leveled constitution.
On our own physical level, the entire solar system can be called a solar monad, with the sun at its heart. The sun, in turn, can be called a solar monad, built up of smaller monads, with its own governing monad at its centre. The human physical body can likewise be called a monad, made up of smaller monads, with perhaps a central monad in the heart or brain. At the same time, every physical entity is animated and guided from inner, subtler levels of its constitution, and each of its more ethereal bodies or souls (or aggregated monads) likewise has its own central nucleus (or monad), with the very highest monad (or monadic essence) in overall control. The human constitution contains the following monadic centers: a divine monad, a spiritual monad, a higher human monad, a lower human monad (which we are at present), a beast monad, and an astral-physical monad. Each of these monads possesses a fund of stored-up evolutionary experience (or ego) and works through an appropriate vehicle (or soul).
Monads are eternal, unitary, individual life-centers, consciousness-centers, deathless during any solar manvantara, therefore ageless, unborn, undying. [They] are spiritual-substantial entities, self-motivated, self-impelled, self-conscious, in infinitely varying degrees, the ultimate elements of the universe.
Every monadic essence, every monad, no matter where or in what period of time, is a learning entity, always advancing from the less to the more perfect. In any one cosmic manvantara it begins its evolutionary journey as an unself-conscious god-spark, passing through all the phases and experiences which that particular manvantara contains, and finishes as a fully perfected god.