The Great Commentary, or Keys to the Unseen, is a commentary on the Quran by Sheikh al-Islam Fakhr al-Din al-Razi (544 AH – 606 AH). The Great Commentary and Keys to the Unseen are two sides of the same coin, as they are two well-known names among scholars and researchers for a single commentary authored by Imam Fakhr al-Din al-Razi. Some scholars have attempted to combine these two names, stating that al-Razi authored his Great Commentary, entitled Keys to the Unseen. This commentary is considered the most important, and indeed the best, of the commentaries belonging to the school of exegesis that adheres to the praiseworthy approach of interpreting based on reason. It is a comprehensive scholarly encyclopedia specializing in the field of Islamic religion in general, and the science of Quranic exegesis in particular. Furthermore, it is a cornerstone of rational Quranic commentaries, representing the pinnacle of intellectual endeavor to understand the Quran. It is a vast repository of rational approaches and theoretical pronouncements on interpretation. It is considered a comprehensive commentary because it combines interpretation based on sound reason and authentic transmission, in addition to encompassing extensive research covering various topics from different fields of knowledge. It is also considered one of the longest and most detailed commentaries, both ancient and modern, offering a comprehensive presentation of opinions and discussions of various beliefs and schools of thought. In it, Imam al-Razi explains the connection between different surahs and verses, elaborates on the cosmology, and addresses fundamental, grammatical, and rhetorical issues, as well as intellectual deductions. His commentary elucidates the meanings and allusions of the Holy Quran, and includes extensive research in various Islamic sciences, such as theology and the sayings of philosophers. He presents the schools of thought of jurists and their arguments regarding verses of legal rulings, champions the Sunni school of thought in creed, refutes the Mu'tazilites and other deviant sects, and refutes their doctrines. He also addresses the philosophers. This book is considered one of the most important, comprehensive, and richest works of Quranic exegesis.