Hegel (August 27, 1770 to November 14, 1831,{sys:(year(now)-1770)} years ago) was a master of German classical idealist dialectical philosophy and a thorough objective idealist. He advocated that ideas are primary, that they continue to develop in logic in the form of pure concepts, then externalize into nature, and finally return to the ideas themselves in the various sciences of spiritual philosophy. In this way, he established a huge system of objective idealism based on ideas and encompassing all sciences. His main contribution in the history of philosophy is to regard contradiction as the truth and essence of everything, and to discuss that dialectics is the unity of opposites. He regarded the entire nature, human society, and human thinking as being in universal connection and development and change. The imthoroughness of his dialectics lies in that his philosophical system as "absolute truth" is absolute and eternal. When Marx and Engels created materialist dialectics, they critically absorbed the reasonable core of dialectics in Hegel's philosophy. His main works include "Phenomenology of Spirit","Logic","Lectures on the History of Philosophy","Outline of the Complete Book of Philosophy", etc. The latter is divided into three parts: "Logical Philosophy","Natural Philosophy" and "Spiritual Philosophy", which is an exposition of its entire philosophical system.