Complexity and the Arrow of Time by

Language: eng
Format: azw3
Publisher: Cambridge University Press
Published: 2013-07-31T04:00:00+00:00

8.6.1 The adjacent possible

Consider a flask of one thousand kinds of small organic molecules. Call these the actual. Now let these react by a single reaction step. Perhaps new molecular species may be formed. Call these new species the molecular “adjacent possible”. It is perfectly defined if we specify a minimal stable lifetime of a molecular species. Now, let me point at the adjacent possible of the evolving biosphere. Once lung fish existed, swim bladders were in the adjacent possible of the evolution of the biosphere. But two billion years ago, before there were multicelled organisms, swim bladders were not in the adjacent possible of the evolution of the biosphere.

I think we all agree to this. But now consider what we seem to have agreed to: with respect to the evolution of the biosphere by Darwinian preadaptions, we do not know all the possibilities. Now let me contrast our case for evolution with that of flipping a fair coin 10000 times. Can we calculate the probability of getting 5640 heads? Sure, use the binomial theorem. But note that here we know ahead of time all the possible outcomes, all heads, all tails, alternative heads and tails, all the 2 to the 10000 power possible patterns of heads and tails. Given that we know all the possible outcomes, we thereby know the “sample space” of this process, so can construct a probability measure. We do not know what will happen, but we know what can happen.

But in the case of the evolving biosphere, not only do we not know what will happen, we do not even know what can happen. There are at least two huge implications of this: firstly, we can construct no probability measure for this evolution by any known mathematical means. We do not know the sample space. Secondly, reason, the prime human virtue of our Enlightenment, cannot help us in the case of the evolving biosphere, for we do not even know what can happen, so we cannot reason about it. The same is true of the evolving econosphere, culture, and history; as I will try to show us, we often do not know ahead of time the new variables which will become relevant, so we cannot reason about them. Thus, real life is not an optimization problem, top down, over a known space of possibilities. It is far more mysterious. How do we navigate, not knowing what can happen? Yet we do. This has very large implications for how we govern ourselves and live wisely when we cannot know all that can happen.

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