Nothing
ParmenidesOne of the earliest western philosophers to consider nothing as a concept was Parmenides (5th century BC) who was a Greek philosopher of the monist school. He argued that "nothing" cannot exist by the following line of reasoning: To speak of a thing, one has to speak of a thing that exists. Since we can speak of a thing in the past, it must still exist (in some sense) now and from this concludes that there is no such thing as change. As a corollary, there can be no such things as coming-into-being, passing-out-of-being, or not-being.[4]
Parmenides was taken seriously by other philosophers, influencing, for instance, Socrates and Plato.[5] Aristotle gives Parmenides serious consideration but concludes; "Although these opinions seem to follow logically in a dialectical discussion, yet to believe them seems next door to madness when one considers the facts."[6]
LeucippusLeucippus (early 5th century BC), one of the atomists, along with other philosophers of his time, made attempts to reconcile this with the everyday observation of motion and change. He accepted the monist position that there could be no motion without a void. The void is the opposite of being, it is not-being. On the other hand, a thing that exists is an absolute plenum and there can be no motion in a plenum because it is completely full. But there is not one monolithic plenum, existence consists of a multiplicity of plenums. These are the invisibly small atoms of the atomists theory, later expanded more fully by Democritus (circa 460 BC – 370 BC). They are a necessary part of the theory to allow the void to exist between them. In this scenario macroscopic objects can come-into-being move through space and pass into not-being by means of the coming together and moving apart of their constituent atoms. The void must exist to allow this to happen or else the frozen world of Parmenides