"The tendency to preserve life and to fight against death is the most elementary form of the biophilous orientation, common to all living substance. Inasmuch as it is a tendency to preserve life and to fight death, it represents only one aspect of the drive toward life. The other aspect is a more positive one: living substance has the tendency to integrate and to unite; it tends to fuse with different and opposite entities, and to grow in a structural way. Unification and integrated growth are characteristic of all life processes, not only as far as cells are concerned, but also with regard to feeling and thinking.

"The most elementary expression of this tendency is the fusion between cells and organisms, from non-sexual cell fusion to sexual union among animals and man. In the latter, sexual union is based on the attraction between the male and female poles. The male-female polarity constitutes the core of that need for fusion on which the life of the human species depends. It seems that for this very reason nature has provided man with the most intense pleasure in the fusion of the two poles. Biologically, the result of this fusion is normally the creation of a new being. The cycle of life is that of union, growth and birth--just as the cycle of death is that of cessation of growth, disintegration, decay."

Erich Fromm, The Heart of Man