When a human being reaches the time for that change which we know as death the consciousness leaves this physical body and goes on with life in bodies composed of the matter of the invisible worlds. Later consciousness parts with the invisible body, and also in due course of time transfers its activities once more to the physical world, appearing again in an infant physical body which serves its purpose until the succeeding physical death. In this alternation from the visible to the invisible, from the grosser to the rarer, from the outer to the inner, from the objective to the subjective the soul finds its possibilities of evolution from lower to higher states of consciousness, each cycle carrying it to a higher point than it has previously attained. The method by which it grows is the acquirement of experience in the physical life, and the working up of this experience into faculties or powers during the life in the invisible worlds. They represent many grades of intelligence and many degrees of effort.
Souls are like children in nature's school.
Millions are in higher grades, hundreds have finished their education and are voluntarily staying back to act as teachers of the rest. These, Theosophy knows as the Masters of the Wisdom. The Path of Perfection Adeptship is the identity of the innermost self of man with the innermost self of the universe, the Atma with the Paramatma, pseudo-individuality is dissolved. The Adept abides in perpetual experience of identity with Universal Spirit. This is Perfection, Nirvana or Salvation - liberation from illusion of separated individuality.