Everything in the world is an illusion. To see things like this is to see them as they really are. To see otherwise is to see them as they are not, to engage in projection, and to become attached to phenomena.
Perceiving an image in a mirror, a reflection in water, a figure in the moonlight, a shadow on a wall, or an echo in a valley, people attached to their own projections cling to phenomena and non-phenomena. Unable to abandon them, they continue to engage in projection and fail to attain tranquility.
—Buddha Sakyamuni, Lankavatara Sutra