>Helene Blavatsky
Author of: The Secret Doctrine
Blavatsky's greatest work is The Secret Doctrine. This book appeared in 1888 in two large volumes, the first concerned with cosmogenesis, the study of the origin and development of the universe, and the second with anthropogenesis, the study of the origins and development of humanity. This book continues in greater detail the themes set forth in Isis Unveiled, its subtitle, The Synthesis of Science, Religion, and Philosophy, expressing the aim of the work.
HPB made it clear that The Secret Doctrine was not written as a revelation but is rather a collection of fragments scattered throughout thousands of volumes embodying the scriptures of the great Asian and pre-Christian European religions and philosophies. Furthermore, she strongly rejected the dogmatic interpretation of any of her work. The reader is asked to study the ideas from this or any other source only in the light of common human experience and reason.
The Secret Doctrine outlines a vast scheme of evolution relating to the universe and to humanity, and to the unseen as well as the seen worlds of manifestation in which life is said to exist in thousands of forms. It is based on three fundamental propositions:
An Omnipresent, Eternal, Boundless, and Immutable Principle on which all speculation is impossible, since it transcends the power of human conception and could only be dwarfed by any human expression or similitude. It is beyond the range and reach of thought.
The Eternity of the Universe in toto as a boundless plane; periodically "the playground of numberless Universes incessantly manifesting and disappearing."
The fundamental identity of all Souls with the Universal Over-Soul, the latter being itself an aspect of the Unknown Root; and the obligatory pilgrimage for every Soul—a spark of the former—through the Cycle of Incarnation in accordance with Cyclic and Karmic law.
https://www.theosophical.org/component/content/article/25-online-resources/online-leaflets/1796-hp-blavatsky-and-her-writings