This text explores the philosophical and historical evolution of the fundamental concepts of immutability and eternity in human thought, tracing them from prehistoric times to ancient Greece. The author notes that even archaic societies distinguished between transient, changing phenomena and realities perceived as permanent or eternal. However, a significant conceptual shift occurred with the ancient Greeks, who refined the notion of eternity specifically as a state of absolute and complete immobility. A crucial aspect of this reflection is the realization that this understanding of immutability was not based on direct empirical experience, as humans do not encounter anything truly motionless in the natural world. Instead, it was a theoretical construct or conjecture, evidenced linguistically by the necessary use of negation. Furthermore, the original meaning of the word eternity did not signify an absence of change, but rather a very long duration spanning many ages. The text thus critically examines how our perceptions of what lies beyond the reach of time and becoming were shaped throughout history.