There is a saying,

What does this mean?

First, the Tree tells us that whatever we know about the Universe, we know through the nature of our minds. The awareness (as Tiphareth) has no direct access to the world of Action (Malkuth), as it is mediated by the images we perceive in Yesod; the sum total of sensory input accessible to it, combined with how our thoughts and feelings interpret and modify them. This was recognised in the East – so the Buddhists call the apparent world ‘Maya’ – at least as far back as 500 B.C.E., and in the West for a roughly similar time. The Greeks used the simile of sediment in a bottle of wine - it was called the ‘hypostasis’ (that which lies beneath the wine) – as the unknowable reality behind the world of appearance. This word appears in the New Testament in the letter to the Hebrews, Chapter 11:1 –‘Now faith is the substance of things hoped for, the evidence of things not seen’. That word ‘substance’ means what it did to our ancestors; the unknowable reality behind appearance, and the Greek word is ‘Hypostasis’. It is why, in English, we capitalise the word ‘I’; as a recognition that we are talking about something real, prior to appearance. In German, all nouns are capitalised for the same reason. Although we live in this world of appearance, our true nature is not of this world, but prior to it. That is, what the early Christians meant by Faith is exactly what all mystics, in all times and places, have meant; that somehow this ‘unknowable reality’ behind appearance can be ‘known’. As Jesus said, ‘The Kingdom of Heaven is within you’ (Luke 17:21)

When Descartes decided to rebuild philosophy from first principles, he recognised that everything he knew came from the detection and interpretation of events presented to his consciousness; but that this knowledge was necessarily flawed. He knew it must relate in some way to the ‘real’ (that is, substantial) world, but that anything and everything was open to misperception, misunderstanding, misinterpretation, misrepresentation… and all the other deliberate or accidental errors our minds are subject to. He recognised that, for example, if he were looking at an apple, that the ‘real’ apple could not be red, because that is a quality of the apple, and therefore part of the apparent world. The same applies to height, length, breadth, taste, smell, and any other detectable quality, including location in space, duration in time, and even separateness from other aspects of the apparent world. That is, the ‘real world’ is a monad; sizeless, locationless, qualityless – something that can only be described by what it is not. Descartes decided that this world must be, effectively, unknowable in itself, but that whatever could be known would only be through measurement of the apparent world. In this, he plays an often unrecognised part in the development of the scientific method.

However, the mystics say that there is another way; by direct knowledge of the Real through mystical experience. I recommend ‘Mysticism and Logic’, by Bertrand Russell, for an examination of these two modes of experience. While I do not agree with everything in the book (for example, his conflation of mysticism with intuition and instinct), there is much to meditate upon.

Two questions arise from the foregoing;

1. If the Real World is a monad, why and how does it generate appearances of such bewildering variety? – and,
2. If Malkuth is inaccessible to consciousness, how does the mystic come into contact with it?

The answer to the first comes in two sections;

1. Why is appearance 'different' to the Monad?     A somewhat glib (but nevertheless as accurate as such metaphysical subjects get) answer. Because the states of consciousness in which we ordinarily experience the world are so limited, the only way that even a shadow of the Real world can be presented to us is as an effectively infinite universe existing and evolving through time and space. The appearance is not an illusion; it is illusory, but to some degree portrays the unknowable reality behind it.
2. How is variety generated?     For one to become many, there must be a stage or stages between the monad and the world apparent to our awareness, equally undetectable, but (in a sort of fractal manner), dividing and subdividing the creative process of the monad until the universe, in all its variety, is presented to us.

In Qabalah, the monad is primarily represented by Kether, (as Atziluth, the World of Emanation). The fractalisation process is brought about in Chokmah and Binah (as Briah, the World of Creation). Our awareness has immediate access to the Sephiroth of Yetzirah below the veil and at least an indirect access to those above it, as the world of appearance.

In ‘The Republic’, Socrates describes people who live chained to the wall of a cave. Their only illumination comes from a fire behind them, which casts shadows on the wall when people pass in front of it. As this is all the world they know, they attribute reality to the shadows. This is analogous to the Tree of Life. Kether is the pure brilliance of Emanation; Chokmah and Binah, as Briah, manipulate that light. Our awareness (in Tiphareth) looks onto the world of forms, (the ‘Treasure-house of Images’ as Yesod is sometimes called), and takes the appearance ‘cast’ by Briah onto the ‘unillumined mirror’ of Yesod for Reality. What is required to escape this illusory world is to turn the awareness around, and look at what is creating it. In Greek, the word for this ‘turning around of the mind’ is Metanoia (which is translated as repentance - ‘thinking again’, and taken to mean feeling sorry – not, in itself, reprehensible, but a long way from the real meaning).