The concept that the world is an illusion is controversial in Buddhism. The Buddha does not state that the world is an illusion, but "like" an illusion. In the Dzogchen tradition the "perceived reality" is considered literally unreal, in that objects which make-up perceived reality are known as objects within one's mind, and that, "as we conceive them", there is no pre-determined object, or assembly of objects in isolation from experience that may be considered the "true" object, or objects. As a prominent contemporary teacher puts it: "In a real sense, all the visions that we see in our lifetime are like a big dream [...]". In this context, the term "visions" denotes not only visual perceptions, but appearances perceived through all senses, including sounds, smells, tastes and tactile sensations.