This preprint introduces the Principle of the Uninhabited Future, a conceptual and ontological hypothesis concerning the structure of time. The principle proposes that future moments do not possess ontological existence prior to their actualization, while past and present moments do. As a consequence, the existence of observers or travelers originating from the future is considered impossible. The hypothesis offers a coherent explanation for the absence of future-originating time travelers without invoking technological, ethical, or causal prohibitions.