Abstract: In the Tang Dynasty, the commentators, LI Shan and Wuchen (the Five Officials) interpreted the line: floating clouds obscuring the bright sun. The line, from the poem: Xingxing Chong Xingxing (The Endless Road of Farewell), is viewed as a metaphor for slanderous ministers blocking worthy officials. Their reading presupposed the existence of a stable, long-circulating symbolic pattern: the line representing slanderous ministers blinding the sovereign--dating back to the pre-Qin-dynasty era (PQDE). However, a survey of textual instances of the line from the PQDE through the Tang Dynasty reveals a more complex evolution. During the transition from the PQDE to the Han Dynasties, although this imagery had appeared in Chu Ci (The Elegies of State Chu) as an incipient political metaphor, it had not yet solidified into a fixed expression denoting a gloomy political situation. It was roughly after the Eastern Han Dynasty that the line equal to slanderous ministers obscuring the sovereign gradually became dominant. This semantic shift of the line was deeply rooted in the intellectual context of the Han Dynasty. Under the influence of qi (vital energy)-based cosmology and the doctrine of heaven-human interaction, floating clouds were reconceptualized as evil qi, reflecting a profound transformation in the Han Dynasty’s philosophy of nature. Accordingly, based on their modes of meaning-presentation and degrees of semantic fixation, imagery from the line can be categorized into two types: the bixing (metaphorical-allegorical) type and the chenwei (divinatory-ominous) type. These two types sometimes overlapped and competed for interpretive authority. LI and the Five Officials’ reading of the line exemplifies the outcome of the chenwei type’s successful bid for such discursive power.