This is called Aristotle’s Illusion because it was first recorded by the ancient Greek philosopher Aristotle (see Aristotle & Ross 2001). Although it is called an illusion, one might think that it is actually a case of hallucination. In cases of illuson, one perceives an external object, but misperceives some of its properties. In cases of hallucination, one has the perceptual experience of an object which doesn’t exist. Here, it might be argued that we are experiencing a second object which does not exist in reality, hence suggesting that this is a case of hallucinatory experience.