Ancient Greek philosophers were behind the establishment of many philosophical questions that puzzle philosophers to this day. Parmendies, one of these early philosophers, was the founder of a group of brilliant thinkers known as the Eleatics. Much of Parmenides' works of literature no longer exist, lost over the course of time. But one important poem, "Nature," has survived to be studied, and much respected today. In this poem, Parmenides claims that change is not possible and existence is changeless and uniform. Parmenides has a valid argument as well as some evidence to support his claim.
What led Parmenides to believe that change does not exist and that existence lasts forever? Parmenides maintains that whatever one speaks about or thinks about must in some sense exist. If it did not exist then it is nothing, so one would be speaking or thinking about nothing, which would be empty. It can be assumed that the existing thing did not just come into existence because saying that would allude to a time when it did not exist. Parmenides then infers that existing things are eternal because they cannot go out of existence. Parmenides concludes his argument by claiming that change is an illusion, on the grounds that a change in a thing implies that there was a time when the thing-as-changed did not exist.
Parmenides argument takes as a premise that whatever one thinks or speaks about exists. If this is true then why aren't there any unicorns roaming around, money trees growing on every corner, or any other common fantasies coming to fruition? If nothing ever changes then what do you call the transformation of a caterpillar into a butterfly? Parmenides also makes the assumption that thinking or speaking about nothing is empty. This is wrong because nothing is something in itself just like the number zero represents "nothing" but it is still a number. Parmenides fails to adequately to explain the correlation between reality, existence and perception.