This lesson introduces students to the foundational principles of al-Jarḥ wa al-Taʿdīl, emphasizing its role as a critical methodology for preserving the authenticity of the Sunnah. It explains that the objective of this discipline is not to judge narrators as individuals, but to evaluate narrations based on the reliability of those who transmit them. The lesson carefully defines key technical concepts such as taʿdīl (affirmation of reliability), ʿadālah (moral uprightness), and ḍabṭ (precision in transmission), clarifying how each functions within the broader framework of ḥadīth criticism. Linguistic foundations are explored to show how technical meanings are rooted in Arabic usage, helping students understand why certain terms were adopted by the scholars of ḥadīth. The lesson further examines nuanced issues such as the role of taqwā and murūʾah in narrator evaluation, the scholarly disagreement surrounding the definition of bidʿah, and the dangers of unrestricted criticism. By highlighting historical debates—particularly those involving major Sunni theological schools—the lesson demonstrates the importance of methodological restraint and contextual awareness in al-Jarḥ wa al-Taʿdīl. Students are guided to appreciate that this science is narration-centered rather than personality-centered, and that misuse of its principles can undermine the integrity of Islamic scholarship itself. Overall, the lesson equips learners with both conceptual clarity and critical caution in approaching the evaluation of ḥadīth transmission