l The ability of evolution comes from inheritance and variation. Inheritance is the essential property of life, but variation is not essential property of life. There is no difference between variation of non-life and that of life, maybe except their names.

l It only proves how complex life is that the important phenomena in living systems are predominantly qualitative, not quantitative. Research of quantitative of life, however, is increasing rapidly by the development of science.

In conclusion, the Cluster Definition of life is not able to separate life from non-life. Sometimes, it is said some non-life are vital like flame, river or the Earth, just because they have some of upper characteristics.

Structural Definition of Life and Molecular Biology

Friedrich Von Engels said, “Life is the existing status of proteins. The essence of the existing status is the continual reconstruction of chemical component of these proteins by themselves” (Marx, & Engels, 1994).

After 1950s, this view changed by the discovery of double helix of DNA and its inheritance. Nucleic acid which is able to reproduce itself and carry hereditary information began to be treated as the molecular basis of life.

At the beginning, molecular biology was expected to help us to discover the essence of life. During a long period after the revolution of molecular biology, however, most philosophers and biologists seemed to have forgotten the question of the essence of life. Why?

The major method of molecular biology is reductionism aiming at component. This method was successful in finding the essence of matter. Material consist of molecule, molecule consist of atom. This reductionism have found generality of all material which is a few kinds of components and their simple combination.

The generality of life is special ways of combination of positive feedback and negative feedback, which determine the characteristics of life. The generality of life have nothing to do with components. Molecular biologists, therefore, cannot find the generality of life by reducing simply to components like physicists. What is more, molecular biology is not able to tell whether chemical ways are necessary conditions of the origin of life.

Ⅲ. Progress of System Theories

System theories pay attention to structure of system instead of components. So it is not surprised that system theories plays important role in research of life. The starting point of system theories is the belief that function is determined by structure. The reason why life has different characteristics with non-life is that life has different structure.

Early system theories was not influential because they did not find relations of feedback. Later, negative feedback was discovered. As a result, the Cybernetics progressed quickly. After that, the Dissipative Structure Theory and the Hypercycle Theory discovered some phenomena about positive feedback, so they won the Nobel Prizes.

System theories have not provided a correct answer of the essence of life yet. The Dissipative Structure Theory noticed that order and self-organization are possible when system is in the state of non-equilibrium by consuming energy (