"The question, at which point we draw the line between living and non-living is not a scientific question.The line between living and non-living at the beginning of evolution is arbitrary, just as the line between human and non-human primates at the end of evolution is arbitrary.The task of science is not to define the exact position of the line but to understand how it came to be crossed." Freeman Dyson, Infinite in All Directions, p. 54.

The study of artificial life (A-Life or AL) assumes that life as we know it is but one part of life as it could be, and seeks to explore the "space of possible life". If biology for the most part has studied the material basis of life, artificial life is concerned with the formal basis of life, which it views as a property of the organization of matter rather than of the matter which is so organized. Thus the strong claim of artificial life is not to be a simulation of biological systems so much as an autonomous life form. (with rights?)

Stuart Kauffman's Origins of Order distinguishes between properties essential to life itself and properties now essential to our life. For him, grammar models are testbeds for the locus of law in deeply historical sciences such as biology.  

The study of artificial life currently focusses on synthetic " bottom up" approaches, in which life is emergent behaviour based on local rules (as opposed to global ones) (see local / global) and on the feedback between ongoing dynamics between genotypes and phenotypes. It assumes that "living organisms are nothing more than complex biochemical machines", and that living systems are "highly distributed and quite massively parallel." (Langton. p. 5) The claim of A-life is that the "artificial" in Artifical Life refers to the component parts, not the emergent processes. If the component parts are implemented correctly, the processes they support are genuine--every bit as genuine as the natural processes they imitate. (Langton p.33) Thus the flocking in computer boids is true flocking. 

The entire field of A-life and complexity has been criticized as based on a seductive syllogism based on mathematics and computer graphics that goes like this: There are simple mathematical rules that when followed by a computer give rise to extremely complicated patterns. The world also contains many similar patterns. conclusion: simple rules underlie many extremely complicated phenomena in the world. With the help of computers, scientists can root them out. (see article in Science 1994 by Naomi Oreskes)

A working definition of life:

1. Life is a pattern in space-time rather than a specific material object.
2. Self-reproduction (in itself or in a related organism)
3. Information storage of a self- representation 4. A metabolism that converts matter/ energy.
5. Functional interactions with the environment
6. Interdependence of parts
7. Stability under perturbations of the environment
8. The ability to evolve.
9. Growth or Expansion.