The third important book of the Han period was the _Lun Hêng_ (Critique of Opinions) of Wang Ch'ung, which appeared in the first century of the Christian era. Wang Ch'ung advocated rational thinking and tried to pave the way for a free natural science, in continuation of the beginnings which the natural philosophers of the later Chou period had made. The book analyses reports in ancient literature and customs of daily life, and shows how much they were influenced by superstition and by ignorance of the facts of nature. From this attitude a modern science might have developed, as in Europe towards the end of the Middle Ages; but the gentry had every reason to play down this tendency which, with its criticism of all that was traditional, might have proceeded to an attack on the dominance of the gentry and their oppression especially of the merchants and artisans. It is fascinating to observe how it was the needs of the merchants and seafarers of Asia Minor and Greece that provided the stimulus for the growth of the classic sciences, and how on the contrary the growth of Chinese science was stifled because the gentry were so strongly hostile to commerce and navigation, though both had always existed. There were great literary innovations in the field of poetry. The splendour and elegance at the new imperial court of the Han dynasty attracted many poets who sang the praises of the emperor and his court and were given official posts and dignities. These praises were in the form of grandiloquent, overloaded poetry, full of strange similes and allusions, but with little real feeling. In contrast, the many women singers and dancers at the court, mostly slaves from southern China, introduced at the court southern Chinese forms of song and poem, which were soon adopted and elaborated by poets. Poems and dance songs were composed which belonged to the finest that Chinese poetry can show--full of natural feeling, simple in language, moving in content.