Predating computers
Before cyberspace became a technological possibility, many philosophers suggested the possibility of a virtual reality similar to cyberspace. In The Republic, Plato sets out his allegory of the cave, widely cited as one of the first conceptual realities. He suggests that we are already in a form of virtual reality which we are deceived into thinking is true. True reality for Plato is only accessible through mental training and is the reality of the forms. These ideas are central to Platonism and neoplatonism.
Another forerunner of the modern ideas of cyberspace is Descartes’ thought that people might be deceived by an evil demon which feeds them a false reality. This argument is the direct predecessor of the modern ideas of brain in a vat and many popular conceptions of cyberspace take Descartes’ ideas as their starting point.
Visual arts have a tradition, stretching back to antiquity, of artefacts meant to fool the eye and be mistaken for reality. This questioning of reality occasionally led some philosophers and (especially) theologians to distrust art as deceiving people into entering a world which was not real (see Aniconism). The artistic challenge was resurrected with increasing ambition as art became more and more realistic with the invention of photography, film (see Arrival of a Train at a Station) and finally immersive computer simulations.