Hegel's Science of Logic has received less attention than his Phenomenology of Spirit, but Hegel himself took it to be his highest philosophical achievement and the backbone of his system. The present book focuses on this most difficult of Hegel's published works. Beatrice Longuenesse offers a close analysis of core issues, including discussions of what Hegel means by 'dialectical logic', the role and meaning of 'contradiction' in Hegel's philosophy, and Hegel's justification for the provocative statement that 'what is actual is rational, what is rational is actual'. She examines both Hegel's debt and his polemical reaction to Kant, and shows in great detail how his project of a 'dialectical' logic can be understood only in light of its relation to Kant's 'transcendental' logic. This book will appeal to anyone interested in Hegel's philosophy and its influence on contemporary philosophical discussion.