ABSTRACT

We shall show that, in a "multiuser" world, strict immortality in the long term is a contradiction in terms. Next best, then, what is a good strategy for at least some part of me to still be present in a large proportion of samples of the future? Perhaps long individual life, many identical clones, continual repair, sexual reproduction, uploading myself to the cloud, or what else?

Even if for sake of argument I grant that "survival of the fittest" is a mere tautology, so that `fittest' just means "whoever survives" (a fatalistic que sera sera; cf. analogous tautological constructs such as "the invisible hand of the marketplace"), I am still left with the fundamental question, What kinds of structure have what it takes to survive in my current environment? In other words, for a given natural or artificial environment, what properties of a complex structure give it a chance to enjoy permanence in it? It is remarkable, but perhaps not too surprising, that this problem may have quite different solutions depending on the time scale one has in mind (as we shall see, there are "greedy" strategies that can promise short-term permanence but virtually guarantee long-term disappearance).

'Apparition' and 'permanence' are key features of all sorts of emergent systems-and these are found virtually whenever there is available an entropy pump. Lifelike systems are emergent systems that have been caught in a special kind of positive-feedback loop: a runaway (at least for a while) loop with branching tracks, so that from the same initial conditions different "historical developments" are potentially available.

Evolution may be seen as a special case of emergence, namely, the development and interplay of a tangled hierarchy of emergent systems some of which are lifelike. We shall be specially interested in the nature of the entropy pumps on which emergent systems are dependent, and in the hierarchy of entropy pumps|the "entropy cascade"-that drives evolution. In this context, we shall present a novel way to look at both entropy and computation.

BIOGRAPHY

Tommaso Toffoli is a professor of electrical and computer engineering at Boston University where he joined the faculty in 1995. He has worked on cellular automata and the theory o of artificial life (with Edward Fredkin and others), and is known for the invention of the Toffoli gate.

Research Interests

• Fundamental connections between physics and computation
• Fine-grained modeling of physics-like systems technology (cellular automata machines) and methodology (programmable matter)
• Personal knowledge structuring

Honors, Awards, and Editorships

• Fellow, IEEE
• Member, Editorial Board: Complex Systems, Journal of Cellular Automata, International Journal of Unconventional Computing