Simulations, Realizations, and Theories of Life.

Abstract

The phrase as interpreted by participants of this workshop, includes not only simulation, but also In the area of artificial intelligence, Searle 2 0 has called the simulation school weak A I and the realization school A I . The hope of strong artificial life was stated by Langton 1 0 : We would like to build models that are so lifelike that they would cease to be models of life and become examples of life themselves. Very l i t t le has been said at this workshop about how we would distinguish computer simulations from realizations of life, and virtually nothing has been said about how these relate to theories of life, that is, how the living can be distinguished from the non-living. The aim of this paper is to begin such a discussion. I shall present three main ideas. First, simulations and realizations belong to different categories of modeling. Simulations are metaphorical models that symbolically stand something else. Realizations are literal, material models that implement functions. Therefore, accuracy in a simulation need have no relation to quality of function in a realization. Secondly, the criteria for good simulations and realizations of a system depend on our theory of the system. The criteria for good theories depend on more than mimicry, e.g., Turing Tests. Lastly, our theory of living systems must include evolvability. Evolution requires the distinction between symbolic genotypes, material phenotypes, and selective environments. Each