The concept of a rational horizon implies a logical and reasonable limit or perspective. The antonyms, therefore, would be words that connote irrationality and illogic. These words might include "chaotic," "sporadic," "random," "illogical," "inconsistent," "unpredictable," and "haphazard." Other antonyms might include "emotional," "whimsical," "unreliable," "unreasonable," and "capricious." These words suggest a lack of structure, reason, or order, and imply a view that is influenced by subjective and unpredictable emotions, rather than a steady and grounded point of view. When considering the antonyms of rational horizon, it becomes clear that the concept of rationality is closely tied to structure, order, and predictability.