Qirqisani devotes a great portion of the first treatise to attacks upon
Rabbinic Judaism. In the last chapter, he also draws a sad picture of the spiritual condition of Karaism in his time. "You can scarcely find two Karaites of one and the same opinion on all matters; upon almost any point each has an opinion different from those of all the rest." He deplores the neglect by the Karaites of the study of rabbinical literature, which, according to him, would furnish them with weapons for their controversies with the Rabbanites. Here, Qirqisani is referring to the discrepancies frequent in
haggadic and
hekhalot literature such as the ''
Shi'ur Qomah'', which, indeed, he often uses in his attacks against the Rabbanites. The second treatise, of twenty-eight chapters, discusses the duty of applying critical methods to study religious matters. Qirqisani is the first Karaite known to have firmly believed in the study of the sciences. He criticizes those who, although accepting the fundamental principle of independent inquiry and research, are against the demonstrative sciences of
dialectics and philosophy. Reason is the foundation upon which every article of faith is based and all knowledge flows. The third treatise, of twenty-three chapters, is a critical review of adverse religious sects and Christianity. In the seventeenth and eighteenth chapters, Qirqisani refutes the doctrine of
gilgul (metempsychosis), though among its exponents was
Anan ben David, who wrote a work on the subject. For Qirqisani, the solution to the question much debated by the
Muʿtazili mutakallimūn concerning the punishments inflicted upon children is not to be found in transmigration but in the belief that compensation will be given to children in the future world for their sufferings in this. In the fourth treatise, Qirqisani expounds, in sixty-eight chapters, the fundamental principles leading to the comprehension of the particular religious prescriptions. The remaining treatises are devoted to the precepts, arranged in systematic order. Qirqisani quotes the views of the earliest Karaite authorities such as Anan ben David,
Benjamin Nahawandi, and
Daniel al-Qumisi, which he often refutes. Belonging to the ''Ba'ale haRikkub'' or Karaite expounders of the Law, he is particularly severe in his views on the
laws of incest. He combats the opinion of his contemporary Rabbanite Jacob ben Ephraim al-Shami, who permitted marriage to the daughter of one's brother or sister. Qirisani claims that natural knowledge and
Greek philosophy originated with
Solomon. ==Extant manuscripts==