There is true knowledge.  Learn thou it is this:  To see one changeless Life in all the Lives, And in the Separate, One Inseparable. The Bhagavad-Gita, Book 18.

This fundamental belief in unity leads naturally to the further belief that all things about us are but forms or manifestations of the one divine life, and that these phenomena are fleeting and impermanent, although the spirit which informs them is immortal and endures.  In other words, it leads to the belief that “the Ideal is the only Real.”

Further, if unity lies at the root of things, man must have some share of the nature of God, for he is a spark of the Divine.  Consequently, man is capable of knowing God through this godlike part of his own nature, that is, through his soul or spirit.  For the mystic believes that as the intellect is given us to apprehend material things, so the spirit is given us to apprehend spiritual things, and that to disregard the spirit in spiritual matters, and to trust to reason is as foolish as if a carpenter, about to begin a piece of work, were deliberately to reject his keenest and sharpest tool.  The methods of mental and spiritual knowledge are entirely different.  For we know a thing mentally by looking at it from outside, by comparing it with other things, by analysing and defining it, whereas we can know a thing spiritually only by becoming it.  We must be the thing itself, and not merely talk about it or look at it.  We must be in love if we are to know what love is; we must be musicians if we are to know what music is; we must be godlike if we are to know what God is.  For, in Porphyry’s words:  “Like is known only by like, and the condition of all knowledge is that the subject should become like to the object.”  So that to the mystic, whether he be philosopher, poet, artist, or priest, the aim of life is to become like God, and thus to attain to union with the Divine.  Hence, for him, life is a continual advance, a ceaseless aspiration; and reality or truth is to the seeker after it a vista ever expanding and charged with ever deeper meaning.  John Smith, the Cambridge Platonist, has summed up the mystic position and desire in one brief sentence, when he says, “Such as men themselves are, such will God Himself seem to them to be.”  For, as it takes two to communicate the truth, one to speak and one to hear, so our knowledge of God is precisely and accurately limited by our capacity to receive Him.  “Simple people,” says Eckhart, “conceive that we are to see God as if He stood on that side and we on this.  It is not so:  God and I are one in the act of my perceiving Him.”

This sense of unity leads to another belief, though it is one not always consistently or definitely stated by all mystics.  It is implied by Plato when he says, “All knowledge is recollection.”  This is the belief in pre-existence or persistent life, the belief that our souls are immortal, and no more came into existence when we were born than they will cease to exist when our bodies disintegrate.  The idea is familiar in Wordsworth’s Ode on the Intimations of Immortality.