also used to develop other philosophical concepts, such as Valberg's personal horizon: what this world would be internal to if this were all a dream. In recent years of dream research, the argument of characterizing dreaming as a simulation has become widely accepted, as well as creating theories about the purpose and functions of dreaming. In fact, dream researcher Tore A. Nielsen wrote in his 2010 paper "Dream analysis and classification: The reality simulation perspective" that the idea that dreaming is a complex simulation of the world in consciousness during sleep may be a conception of dreaming and simulated reality that many dream researchers would have a hard time coming to accept. As well, dreams place us in this virtually simulated reality that places many characters and people in our lives in the dream. If dreaming was to be a simulated reality, the question arises whether that can be used to describe to social reality that the dream allows us to be in too. Lucid dreaming is characterized as an idea where the elements of dreaming and waking are combined to a point where the user knows they are dreaming, or waking perhaps. The idea of lucid dreaming also poses evidence to the dream argument, the idea that dreaming and being awake are indistinguishable, because one knows they are dreaming in a lucid dream. They control the characters in the dream and the plot of what is happening to them in the dream. Lucid dreams could be the reality that we all think is a dream which would then make our reality now the dream. Existence of simulated reality unprovable in any concrete sense Known as the idea of Nested Simulations: the existence of simulated reality is seen to be unprovable in any concrete sense as there is an infinite regress problem with the argument: any evidence that is directly observed could be another simulation itself. Even if we are a simulated reality, there is no way to be sure the beings running the simulation are not themselves a simulation and the operators of that simulation are not a simulation. " involves a simulation or an entity in the simulation, creating another instance of the same simulation, running it and using its results" (Pooch and Sullivan 2000). In August 2019, philosopher Preston Greene suggested that it may be best not to find out if we're living in a computer simulation