While his mother "urged him to develop a noble heart worthy of a samurai's son,"[1] his grandmother supported him in his study of the Chinese language.

[2] In his early teens, Ansai returned home, and after several years was finally permitted to enter the Myōshin-ji temple of the Rinzai Zen sect in Kyoto for further study.

At twenty eight, he returned to Kyoto, and under the patronage of Nonaka Kenzan, was able to continue his Neo Confucian studies, as well as begin to publish his own materials.

With the production of his first work Heresies Refuted (Heikii, 1647), an outright rejection of Buddhist faith, Ansai fully embraced "the One True Way" of Neo Confucianism.

[3] After his first publication, Ansai spent the remaining thirty-five years of his life writing, publishing, editing, annotating, and punctuating Confucian and Shinto texts (that accumulated to over two thousand pages).

Ansai also frequently went to Edo, to give lectures on Cheng-Zhu school of Neo-Confucianism in front of a large number of daimyōs.

"[7] Such prominent Neo-Confucian scholars as Kinoshita Jun'an, Asami Keisai, Miyake Shōsai, and Satō Naokata were included amongst Ansai's followers of the Kimon school.

For tutoring Masayuki for six out of the twelve months of the year, Ansai was given a salary of 100 gold ryō, two seasonal garments, and one haori coat.

Masayuki proved to be Ansai's intellectual equal, helping him compile five different works: two gazetteers for the Aizu domain, and three Confucian texts: Gyokusan kōgi furoku (Appendix to Zhu Xi's lecture at Yushan), Nitei jikyōroku (Record of the two Cheng's political teachings), and the Irakusanshiden shinroku (Record of the mind-heart).

Due to this, Buddhism contained no theory of mind-heart, and thus, was inadequate for cultivating the mind[10] (both of which were integral to Ansai's ethical thought).

From Ansai's Neo-Confucian perspective, the mind was full (being inherently imbued with the concepts of the Five Relationships and the Five Virtues), not empty (as he believed Buddhism perceived it).

[12] Ansai's teachings were seen to be part of a larger Neo-Confucian trend of the early Tokugawa period, referred to by Abe Yoshino as the rigaku (school of principle).

Zhu Xi saw this fulfillment of potential as the ideal state of human existence, and only possible to achieve if one were to obey one's allotted moral duty, given their relative position in society.

Xi believed that fulfilling one's proper social role was a means of understanding the universal principle of human morality (li).

[16] Like Zhu Xi, Ansai firmly believed that an individual's moral duties reflected his specific social position (meibun).

"[citation needed] Reverence was the means by which one achieved the desired end of self-cultivation, necessary to fulfill the moral duties prescribed to an individual by their rigid, social obligations.

[20] Because cosmologically everything was interconnected, Ansai believed that the actions of an individual (in a similar manner to modern chaos theory) affect the entire universe.

He stressed the Confucian concept of Great Learning, in which a person's actions (the center of a series of concentric circles) extend outward toward the family, society, and finally to the cosmos.

There are five steps which Zhu Xi advocated to perfect these relationships (and virtues): "study wisely, question thoroughly, deliberate carefully, analyze clearly, and act conscientiously."

Departing from Zhu Xi (who saw humaneness as the most important virtue), Ansai believed that maintaining the social order (through duty to one's lord) was the highest responsibility that one had to fulfill.

His Yamato shōgaku (Japanese Elementary Learning), published in 1658, although more focused on general social customs, marks a turning point in Ansai's thought, with its inclusion of various Shinto elements.

[23] In the latter part of his life, Ansai began a project of combining Neo-Confucian morality (based on Zhu Xi) with the religious elements of Shinto.

[31] Due to his belief in this unity, Ansai challenged the traditional Confucian notion of the Mandate of Heaven, where a ruler was held accountable for the welfare of his subjects, and could lose his legitimacy if he did not act in proper accord.

[32] In his book Tokugawa Ideology, Herman Ooms describes Ansai's analysis of Shinto texts as being grounded in "hermeneutic operations", proceeding along four levels of interpretation.

The last level was anagogical, whereby Ansai argued for the supremacy of the Japanese nation (relative to all others), using his own interpretations of Shinto texts.

"[33] Yamazaki Ansai was part of a larger movement in the early Tokugawa era that revived and helped proliferate Neo-Confucian thought in Japan.

[34] He was the first to introduce the writings of the Korean Neo-Confucian scholar Yi T'ogeye to Japan, and was instrumental in popularizing Zhu Xi's thought (partly due to his connections with the government).

After Ansai's death, his students continued to preach some form of his Confucian or Suika Shinto thought, to both commoners and Bakufu officials alike.