John H. Holland: Emergence. Oxford University Press Paperback 2000

An inspiring and accessible book on the science of making much from little. Holland is a foremost computer scientist, ingenius thinker and a brilliant writer. Guided by the rigorous mind of a scientist, with the skills of a master communicator, together with the inner call for wisdom, characteristic of true thinkers, Holland presents a forceful elaboration of a theme which is ever-present and ubiquious, fundamental to life, yet "more wondered at than analysed" (p. 3).

Using board games and ant colonies as a spring board, Holland demonstrates how simple rules can generate tremendous complexity. "Despite the limited reportoire of the individual agents - the ants - the colony exhibits a remarkable flexibility in probing and exploiting its surroundings. Somehow the simple laws of the agents generate an emergent behavior far beyond their individual capacities. It is noteworthy that this emergent behavior occurs without direction by a central executive." This is the logic Holland lays out with clarity and with cool. He instructs us to watch for:

• "mechanisms (building blocks, generators, agents) and perpetual novelty (very large numbers of generated configurations)
• dynamics and regularities (persistent, recurring structures or patterns in generated configurations)
• hierarchical organization (configurations of generators become generators at a higher level of organizations)." (p. 9)

Interaction is the key to emergence as Holland describes it. A chief feature of the book is the complete lack of all mysticism which sometimes is brought in once "emergence" is discussed. Holland presents sort of a "reductionist" view of emergence in which we "reduce explanations to the interactions of simple parts" (p. 8). This is a striking and insightful move by Holland: "Reduction has been repeatedly examined in philosophy, and sometimes in the other humanities, but its connection to rule-governed emergence has not been a facet of these examinations" (p. 8).

The book demonstartes how simple rules (such as rules of chess) and simple constitutive elements (such as the different pawns of chess), when interactive over a perior of time, give rise to an astonishing number of alternatives and potential outcomes. This takes mysticism away from the phenomenon of emergence - a wellcome outcome. At the same time Holland's down-to-earth yet subtle description suggests we should be more excited to look for new combinations and patterns of interaction even among simple and familiar constituents of our own field of action.

Holland instructs us to think in terms of models. We use models all the time, Holland stresses, but very often unconciously (uses of rules of thumb being an example). One useful model is a game. Consider this explosive line of though:

"All in all, games are more bushes than trees. The number of leaves (ending configurations) grow very rapidly, even when the branching process is simple. Indeed, it is this bushiness that provides the fascination and unpredictability of games. Consider a board game in which there are ten possible moves (branches) from each configuration (state), including the initial configuration. If the game terminates after two moves, there are 10 x 10 = 10² = 100 distinct ways of playing the game. If the game terminates after ten moves, there are 10¹⁰ = 10,000,000,000 ways of playing the game. Termination after fifty moves - a lenght and number of oppositions roughly equivalent to chess - yields 10⁵⁰ ways of playing the game, a number which substantially exceeds the number of atoms in the whole of our planet Earth." (p. 37)

Here are some key concepts to look for when considering emergence along the holladian lines:

Building blocks. "Much that is bound up in the concept of a building block is captured by the technical definition of a generator, but the aura of meaning that surrounds this concept is considerably larger. Building blocks range from mechanisms in physics to the way we parse the environment into familiar objects".

Models. "This is the concept most important to this study of emergence. The critical steps in constructing a model are selection of salient features (equivalence classes) and laws (generators and transition functions) governing the model's behavor. ... Emergence and innovation cannot be understood without a thorough understanding of models."

Agents. "Most systems that exhibit emergence can be modeled in terms of the interaction of agents. Agents, which can range from 'billiard balls' in a random interaction model to organisms that adapt and learn, offer the quickest route to building models that exhibit emergence." (p. 224-5)

The upshot is:

"Emergence occurs in systems that are generated. ... The whole is more than the sum of the parts in these generated systems. The interactions between parts are nonlinear, so the overall behavior cannot be obtained by summing the behaviors of the isolated components. Said another way, there are regularities in system behavor that are not revealed by direct inspection of the laws satisfied by the components. (p. 225)

John Holland is a top-of-the-line scientist. One thing that makes this book great is that the author does not fall into the trap of scientism and believe that science can prove science can prove everything. Consider the following magnificent words:

"It may be that the parts of the universe that we can understand in a scientific sense - the parts of the that we can describe via laws (axioms, equations) - constitute a small fragment of the whole. If that is so, then there may be aspects of emergence we cannot understand scientifically. Nevertheless, we already know that there are lawful fragments in which we can observe and explain emergence. It is those fragments with which I am concerned." (p. 231)