Some of these characteristics are phenomena instead of essence, some are not special characteristics of life.

l The reason why living processes are especially unpredictable is the complex structure of life. The reason why life can maintain complex structure is the breeding of life.

l Historical connection is due to breeding, too.

l Non-living things can also be unique, variable and being product of natural selection, these characteristics are not owned exclusively by life.

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.