True clairvoyance is that which allows one to see the reality of the spiritual world, that is, to perceive and understand the most subtle aspects of nature and the human soul.
The other kind of clairvoyance, which consists of seeing past or future events, or even the spirits of the astral world, is nothing extraordinary. Almost everyone can acquire it through certain exercises or by taking drugs, but these methods don’t lead very far and even pose great dangers to the psyche.
The only clairvoyance worth seeking is that which can make you a prism of crystal, allowing the light of Heaven to pass through. It is this clairvoyance that Jesus spoke of when he said, “Blessed are the pure in heart, for they shall see God.”
Omraam Mikhael Aïvanhov – From Man to God: Sephiroth and Angelic Hierarchy, Chapter XIV