History study provides a fact that people in one period of time are significantly different from people who lived at any other time. History also tells us that people in one period of time have much commonness with people who lived at any other time. I considered it to be a biased viewpoint to accept the differences while ignore the commonness. For human development, history study has duty to raise awareness of the importance in both difference and commonness.
We have to agree with the statement that obvious differences exist in people who lived in different historical periods. These differences reflected in the way of life, social relations, religious beliefs, cultural and values. As science and technology are developing, so that people use automobile, airplane and passenger ship instead of carriage, hot-air balloon and steamship, in perfect accord with productivity of modern society. People got together as a federation or tribe in the past time to protect themselves, and we established the minimum unit-- family--to maintain the relationship. Different religious beliefs born in different historical periods. Some of them died away with the war in the long history, others had come down from time immemorial but no longer the original. Even if people lived in the some district changed their beliefs in different historical periods. Culture changes roughly coincide with life style. Chinese simplify their traditional festivals and is fascinated with western festivals as Saint Valentine's Day. The long history of human being makes it easy for everyone to find out differences between himself and people who lived at any other time.
However, in many respects, the basic nature and humanity which lasting millions of years have never changed. For instance, development of human science based on the consistent exploration of unknown world. Curiosity promoted Greek philosopher Aristotle developing geocentric, and inspired Copernicus propounding the heliocentric theory. In 1998, observation of the supernova indicates that our universe is accelerating expended. Art and war are other examples. The most famous achievements in human art history show the some hope and beauty without limits of time and districts. The large or small wars in human history because of the some immoderate desire and cupidity. Finally, yearning for a better life is permanent in all period of time. Compared with differences, commonness of human being seems internal but perpetual.
 It is the limit of cognition that caused the illusion that people in one period of time are significantly different from people who lived at any other time in history. People cogitate the society dependent on his or her thinking style and how much information can be used. As communication decreased, less and less information will be spread, and more problems will be exaggerated because of ignorance. People who lost the chance learning from others in history may regard his own problem as unique.
Thinking style can be another factor governs people`s understanding of themselves. Modernist may disagree with the old idea of 'the more sons, the more blessings', but intestate financial products for the some internal reason--make their future life guaranteed. People`s cognition take notice of the obvious differences at first, and hardly touch the internal commonness without enough available information and skillful thinking style. The cognitive limits of history misleading people to exaggeration of themselves and differences.
Study of history solved problems by broadening our vision and knowledge, and awakes the awareness of ignorance. We learn from history both differences and commonness to improve earthly life and avoid the universal mistake. Although, differences give chances to make progress, especially in nature science and technology. I’m still emphasizing the importance of commonness. For instance. There is no wars are alike in the world, but the objective and ends are always the same. We learn from wars for another one or, perhaps, trying to avoid them. Psychology, a study of human psychic history, finds out the similar psycho logic characters in different period of time, and help people overcome the psychological barriers. The study of history is to avoid mistakes even in common while seek development in differences.
We recognized that people in one period of time are significantly different from people who lived at any other time. These differences promote the development of human society. But, we know from the history that the basic nature and humanity of human being have never changed. Study of history should make people aware of the internal commonness so that people will not be confused by ostensible differences.