A thought, or gedanken, experiment is the creation of a simplified, often fanciful, world for the purpose of understanding the implications of a theory. One of the first was Plato’s allegory of the cave, in which Plato postulates that people are only able to sense a part of the universe about them. The allegory explores what that means and implies. The real value of thought experiments is to generate hypotheses that can be tested in the real world.