船山認為明代的覆亡與學術的興衰有關，而正學的沉淪，邪說的泛濫，正是導致社會人心陷溺的主要關鍵。因此，船山博通各家，遍注群籍，試圖恢復儒家的正學，並據此而批判異端，冀能導正學術風氣，而有補於世道。《老子衍》與《周易外傳》是船山最早的兩部著作，前者代表船山對異端之學的態度，後者則奠定了儒家思想的基本體貌。本文認為：船山是用自成一家的易學思想來解釋並批判老子的。兩家思想的不同是，儒家體用皆實，而老子體用皆虛；而在「兩端」的認識上，儒家講「一致」，老子說「抱一」。在船山龐大的思想體系中，有關儒家的正學與異端邪說的判別，大體在此時已然確立，《老子衍》一書正具有這種指標性的地位。

Chuan-Shan considered the. the ebb and flow of learning was associated with the fall of Ming Dynasty and the decline of the pure and legitimate learning and prevalence of perverted views and fallacies were the exact causes of an immoral and deteriorating society. Therefore, Chuan-Shan mastered all schools of thought and devoted himself to reading voluminous books to try to restore the pure and legitimate learning of Confucianism and to criticize the heresies with a view to correcting the academic practice and rectifying the society. Lao Zih Yan and Jhou Yi Wai Jhuan (an unauthorized biography) are the first two writings of Chuan-Shan. The former represents Wang's attitude towards heresies and the latter lays a foundation of the basic styles and views of Confucian thinking. In the author's opinion, Wang exercised his own understanding of The Book of Changes to explain and criticize the thoughts of Lao-tzu, a Chinese philosopher in the Spring and Autumn Period. The difference between these two schools is that the Confucian school is solid both in essence and application and the Lao Tzu school is void both in essence and application. For the knowledge of "both ends," Confucianism stresses consistency and Lao Tzu emphasizes unity. Differences between legitimate learning of Confucianism and heretical views are established mostly at this time. The book of Lao Tzu Yan is an indicative writing manifesting such differences.