Take a piece of genuine crystal for example. If there is a yellow object inside, it appears yellow; if the object is replaced with a cyan, red, or white one, the color of the crystal changes accordingly. Likewise, the mind of a common man is confined to his own fantasy and intellect, and so he sees different appearances of things. However, things exist in a state of suchness, which means that they are neither absolutely empty nor non-empty and that they are neither really existent nor non-existent. If one studies the teachings in depth and does not regress or adhere to anything, one attains the receptivity to the profoundest message that leads to freedom. (The Treatise on the Great Perfection of Wisdom)