What is "simple", "not easy", "variation"

Cosmology, the moon and stars, nature, society, population, all this, they change all the time, this is the "original".Although the universe nature, everything is in a rapidly changing, however, the nature and the change of personnel and has a certain regularity, seemingly chaotic, in the work of nature are cycle back and forth, orderly, systematic, the same is true with the fate of the people, this is "not easy".Because we mastered the "difficult", so, to dialysis the overall law of the universe of heaven and earth, thus can predict the human society, the nature of all things, human beings can undertake specification and master of his own fate, this is "simple"."Variation", "not easy" and "simple", is also theThe I ching"To explain the three principles of everything in the world.