Birthday of Hegel (philosopher born 1770): put forward concept of dialectic and opposites

from Garrison Keillor's Writer's ALMANAC (Minnesota Public Radio):

It's the birthday of philosopher Georg Hegel, born in the city of Stuttgart (1770). He started out as a theologian, particularly interested in how Christianity is a religion based on opposites: sin and salvation, earth and heaven, finite and infinite. He believed that Jesus had emphasized love as the chief virtue because love can bring about the marriage of opposites. Hegel eventually went beyond theology and began to argue that the subject of philosophy is reality, and he hoped to describe how and why human beings create communities and governments, make war, destroy each other's societies, and then build themselves up to do it all over again.
He came up with the concept of Dialectic, the idea that all human progress is driven by the conflict between opposites, that each political movement is imperfect and so gives rise to a counter movement which takes control -- which is also imperfect -- and gives rise to yet another counter movement, and so on to infinity. Friedrich Engels and Karl Marx argued that the most important dialectic of history was between worker and master, rich and poor, and their ideas lead to the birth of Communism.
Hegel wrote, "Genuine tragedies in the world are not conflicts between right and wrong. They are conflicts between two rights." And, "We do not need to be shoemakers to know if our shoes fit, and just as little have we any need to be professionals to acquire knowledge of matters of universal interest."