Abstract: In the Poetics, Aristotle pointed out that ordinary history record couldn't reveal a complete action, due to the chaos of causality in historical phenomena. However, tragedy writers could invent a whole action including the beginning, middle and end to reflect some possibility or necessity. From this perspective, tragedy seems to be more serious and valuable resources than historical records. Polybius adopted a critical and inherited attitude to Aristotle's view, and he believed that an inevitable historical trend existed in his own era, so he wrote about “universal history” involving the whole action from beginning to end, and illustrating everything in clear causal relationship. In the meantime, Polybius insisted that historian should record events truthfully, rather than fabricating plots like tragedy writers. Due to the limitations of the individual and the times, Polybius had no awareness of the influence from cultural and academic tradition on himself, and relied on “fictional” devices to finish his “universal history”. However, he firmly held that the “universal history” pursuing the authenticity and inevitability was superior to tragedy, which imitates reality and reflects some possibility or necessity. The authenticity is the core concept in his “universal history”.

Key words: the universal history, Poetics, authenticity