Sorai was born the second son of a samurai who served as the personal physician of Tokugawa Tsunayoshi (徳川綱吉), who would become the fifth shogun. Sorai studied the Zhu Xi version of Song Confucianism, and by 1690 he became a private teacher of Chinese classics. He went into the service of Yanagisawa Yoshiyasu, a senior councillor to Tsunayoshi, in 1696. He left in 1709 after the death of Tsunayoshi and would turn away from the teachings of Zhu Xi to develop his own philosophy and school. He is credited with the creation of kō shōgi, an unusual form of chess.
Sorai would write several influential works. In them he identified two fundamental weaknesses in the philosophy of Song Confucianism. The first was in the bakufu-domain system, which by the eighteenth century was in trouble. As a result, he doubted whether the reliance on finding an individual's ethical good was sufficient. As such he argued that the political crisis of the time required more than perfecting moral character. Moreover, he saw the ancient Chinese sage-kings as concerned not only with morality but also with government itself. His second disagreement with Song Confucianism was that he felt putting too much emphasis on morality repressed human nature, which was based on human emotion.
However, these weaknesses he felt stemmed not from a deficiency in Confucianism itself, but rather from a misreading of classic works of the Four Books and the Five Classics by Song Confucianists, which he insisted "did not know the old words." Sorai went back to the ancient works for more reliable knowledge, stating "The ultimate form of scholarly knowledge is history." To him, these historical works were the ultimate source, even for an ever-changing present. Sorai thought that study of philosophy began with the study of language. In this he was highly influenced by the Ancient Rhetoric school of the Ming period, which was a neoclassical movement that saw the Qin and Han periods as the model for prose, and the Tang period for poetry. The Sorai school introduced Selections of Tang Poetry, a work thought to have been edited by Li Panlong (李攀竜 1514-70), a founder of the Ancient Rhetoric school, to Japan, where it became very popular. As a result, his school is today sometimes also known as the Ancient Rhetoric (kobunji 古文辞) school. However it differed in that he saw it mostly as a means of accessing the Five Classics. He would also accuse other Confucianists in Japan, such as Hayashi Razan, of relying too heavily on Song sources such as Zhu Xi.
Sorai further differed from the Song Confucian viewpoints in other aspects. One was that the Way was not a predetermined principle of the universe, but rather an establishment of men, of the ancient sages who described it in the Confucianist classic works. These works provided for the Way, which was divided by rites (rei 礼) and music (gaku 楽). The former gave social order, while the latter was inspiration for the heart. In this it directly allowed for the flow of human emotions, something denied by the moralist philosophy of Song Confucianism. Sorai argued for the opposite, allowing one to be enriched through music and poetry. As a result of his teachings in putting emphasis on literature as a fundamental form of human expression, Chinese writing would begin to thrive in Japan, becoming an accepted artistic pursuit. His school would thus produce several such great writers of Chinese composition at that time.
Sorai was furthermore a supporter of the samurai class. Institutions that were once under great leadership will later decline and more able men will be less likely to come to power. The samurai, he felt, were best able to overcome this through a system of rewards and punishment. He also saw problems with the merchant class at the time, which he accused of conspiring to fix prices. He was not, however, a great supporter of the lower classes. He argued, "What possible value can there be for the common people to overreach their proper station in life and study such books ?"