Kitab al-Kafi

''Usul (Fundamentals) al-Kafi''

''Furū al-Kāfī''

''Rawdat al-Kāfī''

Authenticity

"whatever agrees with the Book of God, accept it. And whatever contradicts it, reject it"

Scholarly remarks

• The author stated in his Preface of Al-Kafi:

"You said that you would love to have a sufficient book containing enough of all the religious sciences to suffice the student; to serve as a reference for the disciple; from which those who seek knowledge of the religion and want to act on it can draw authentic traditions from the Truthful —may God’s peace be upon them—and a living example upon which to act, by which our duty to God—almighty is he and sublime—and to the commands of his Prophet—may God’s mercy be on him and his progeny—is fulfilled...God—to whom belongs all praise—has facilitated the compilation of what you requested. I hope it is as you desired."

• Imam Khomeini said:

"Do you think it is enough for our religious life to have its laws summed up in al-Kāfī and then placed upon a shelf?"

أنّ الشيخ الصدوق : قدّس سرّه : لم يكن يعتقد صحّة جميع مافي الكافي
The scholars have made these remarks, to remind the people that one cannot simply pick the book up, and take whatever they like from it as truthful. Rather, an exhaustive process of authentication must be applied, which leaves the understanding of the book in the hands of the learned. From the Shia point of view, any book other than the Qur'an, as well as individual hadiths or hadith narrators can be objectively questioned and scrutinized as to their reliability, and none - not even the Sahaba - are exempt from this.
The main criticism of al-Kafi as the basis for Shia fiqh, comes from prominent Sunni writers who argue that finding some hadiths in al-Kafi proves that the entire Shi'ite school is wrong. Shi'ites in reality do not rest the basis of their entire faith on the complete authenticity of this book. They believe that anything that goes against previously held ideas must not be authentic. They also do not automatically accept some hadiths from al-Kafi that have strong historical proofs.
The Qur'an is far more important to Islamic belief than any hadith book, and Shia scholars have long pointed this out.

Shia view of al-Kafi relative to other hadith books

Kulayni himself stated in his preface that he only collected hadiths he thought were important and sufficient for Muslims to know, and he left the verification of these hadiths up to later scholars. Kulayni also states, in reference to hadiths: "whatever agrees with the Book of God, accept it. And whatever contradicts it, reject it".
The author of al-Kafi never intended for it to be politicized as "infallible", he only compiled it to give sincere advice based on authentic Islamic law, and to preserve rare hadiths and religious knowledge in an easily accessible collection for future generations to study.
Al-Kafi is the most comprehensive collection of traditions from the formative period of Islamic scholarship. It has been held in the highest esteem by generation after generation of Muslim scholars. Shaykh al-Mufid extolled it as "one of the greatest and most beneficial of Shia books." Al-Shahid al-Awwal and al-Muhaqqiq al-Karaki have said, "No book has served the Shia as it has." The father of Allamah al-Majlisi said, "Nothing like it has been written for Islam."