In this book, Ibn Sina explains the latest definitions of logic, its principles and issues. Ibn Sina criticizes the logic of Greek philosophers with all neutrality, and states what they have and what they have, in an easy language and a simplified style. The book also includes poems from the "Ibn Sina" systems that embody his philosophy in life and his vision of graying, wisdom and asceticism, and his poems crowned the "double" poem, which every student of logic advises to memorize it because of the summary of what the great philosopher has reached. One of the advantages of this book is that "Ibn Sina" has written it in its other days, that is, after he killed this field in search and study; Therefore, it is the most important among all other works in logic