Thoreau believed in "simple life" , and believed that the real happiness of human beings was only related to the most basic needs of life. In his own words, "whoever has the cheapest happiness is the richest man. " One of the basic principles of human existence is simplicity, the basic self-preservation that eliminates unnecessary needs. Thoreau believed that the surplus needs of human existence could be bought, and that since these human needs were superfluous, so was the part of the money used to buy the surplus needs. If human beings excessively pursue all kinds of desires, they will waste all kinds of unnecessary time and money, and at the same time, they will lose the true nature of life. The essence of life lies not in the amount of money spent, but in the realization of human values and dignity. When people ignore the superfluous needs of survival, simply live, people even if not rich, but also can obtain the inner fullness.