Chemistry and selection.

Life is the product of chemistry, which obeys deterministic laws, and of natural selection, which operates on variants offered to it by chance, but may, in a number of cases, have been provided with a sufficiently extensive array of variants to be optimizing. Thus, the origin and evolution of life have been largely shaped by the contingency of environmental conditions. The possibility remaining open for consideration is that certain critical conditions are sufficiently reproducible for life to arise and even to evolve into conscious, intelligent beings elsewhere in the universe.