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| Emergence or Us from It
"Emergence" could be a Wheeler word. Like "it from bit," it rings like rather wild speculation about the nature of reality. And like "how do you hold up half the ghost of a photon?" it's not immediately clear exactly what's being proposed. Wheeler thought experiments were never designed to lead away from further scientific progress in understanding the world. By pushing physical concepts to their limits, they open doors to new and possibly fruitful inquiry. Is it possible that emergence could do the same?
Critics of emergence complain that it is either trivial, untestable, or false. Trivial, because it seems obvious that, as systems increase in complexity, they will express new properties not manifest at earlier stages. Thus the critic might complain that emergence just restates the concept of complexity -- and in a less clear, more obscure fashion. Untestable, because how could one ever test whether there is a broad pattern of emergence in natural history? If synthetic claims about emergences up the ladder of complexity can't produce fruitful theories, emergence theories will remain philosophy, not science. And false, if emergentists are claiming that mysterious new things emerge in cosmic history that can't be understood at all in terms of more basic levels. After all, it seems, the success that physics has enjoyed just is success at explaining "new things" in terms of more fundamental laws.
Nevertheless, there may actually be something scientifically interesting in emergence. The Wheeler conference offers a good opportunity to explore what that might be.
Emergence is the anthropic principle (AP) read backwards. Imagine for a moment that Wheeler might turn out to be right about the role of human observers in explaining the genesis and evolution of the universe ("In some strange sense this is a participatory universe," At Home in the Universe, 25). With the AP Wheeler places himself at the end of the process and works backwards, deriving "had to's" from what we know about the outcome. If the speculation is true, the "had to's" derive from the measurement effect in quantum mechanics.
What would happen if we moved Wheeler's eye (At Home, 293) to the front of the line? If it could foresee the process of emergence from Big Bang to humanity, would it be able to derive any "had to's"? There are good reasons to doubt that specific evolutionary outcomes are necessary; but are any patterns in evolutionary history to be expected in advance? Could there be an emergentist necessity that serves as the counterpart to the anthropic necessity posited by Wheeler and others?
Here's a difference: anthropic necessity (if there is such a thing) is driven by quantum mechanics, by the need for a measurer external to the QM system. Emergentist necessity (if there is such a thing) couldn't be explained in quantum terms. In fact, it represents the hypothesis that quantum accounts aren't the whole story. It's the hypothesis that, to put it paradoxically, the whole story can only be told by multiple causal stories at multiple levels -- that the multiplicity of the stories is somehow irreducible.
The paper explores areas of allegedly irreducible phenomena. It asks: If the multiplicity of causal accounts is somehow an ultimate given, what does that tell us about the physical universe? And: in what theoretical framework(s) can we explain this fact (if it is one)?
Wheeler's speculations link QM and AP, the eye at the end of the story. The beauty of his proposal is that it unites the ends of the scale: quantum physics and the human observer -- the beginning and the end of the universe's history. The trouble is, it leaves out the middle. There's no intrinsic reason for anything in the middle, except that you need space and stars and heavy metals and protozoa to get to decent observers. Emergence is the series of thought experiments that ask what it would take to give biology a bigger and more essential place in the overall story.
If any of these thought experiments are right, we'd need to supplement Wheeler's proposal. To "It from Bit," we'd need to add, "Us from It" -- a question to which emergence is part of the answer. But how can one make the ages of natural history more than a means to get to the quantum mechanical measurer? And: when we speak of irreducible levels in the natural world -- levels whose explanations cannot fully be given in terms of the underlying levels, even in principle -- can we avoid putting a roadblock of the most egregious sort in front of the progress of science?
I think the answer is yes. The paper attempts to say why.
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This paper was presented at the 2002 Symposium on Science and Ultimate Reality. For more information, go to:
http://www.metanexus.net/metanexus_online/ultimate.asp
Published 2002.03.13
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