The Big Picture
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dict the laws of physics that we go astray.
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If the world we see in our experiments is just a tiny part of a much bigger
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reality, the rest of reality must somehow act upon the world we do see;
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otherwise it doesn’t matter very much. And if it does act upon us, that im-
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plies a necessary alteration in the laws of physics as we understand them.
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Not only do we have no strong evidence in favor of such alterations; we
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don’t even have any good proposals for what form they could possibly take.
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The burden for naturalists, meanwhile, is to show that a purely physical
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universe made of interacting quantum fields is actually able to account for
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the macroscopic world of our experience. Can we understand how order
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and complexity arise in a world without transcendent purpose, even in the
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face of increasing disorder as implied by the second law of thermodynam-
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ics? Can we make sense of consciousness and our inner experience without
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appealing to substances or properties beyond the purely physical? Can we
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bring meaning and morality to our lives, and speak sensibly about what is
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right and what is wrong?
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Let’s see if we can.
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P A R t F O u R
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COM Pl E x It y
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The Universe in a Cup of Coffee
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W
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illiam Paley, a British clergyman writing at the turn of the
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nineteenth century, invited you to imagine a walk through
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one of Britain’s picturesque heaths. Suddenly your reverie is
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interrupted when you stub your toe against a stone. You would be annoyed,
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thought Paley, but what you wouldn’t do is start wondering where such a
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stone could possibly have come from. Stones are the kinds of things one
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naturally expects to come across while walking through fields.
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Now imagine instead that you notice a pocket watch lying on the
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ground during your walk. Here you have a puzzle— how did it get there?
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Not a difficult puzzle, admittedly; presumably someone dropped it while
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out on a walk similar to your own. Paley’s point was that you would never
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imagine that the watch would just have been sitting there since time im-
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memorial. A stone is a simple lump of material, but a watch is an intricate
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and purposeful mechanism. It is clear that someone must have made it; a
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watch implies a watchmaker.
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And so it is, continues Paley, with so many things in nature. What
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we observe in the form of living creatures in the natural world, he ar-
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gued, is “every manifestation of design”— not only complexity but struc-
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tures that are obviously attuned to some specific purpose. Nature, he
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concluded, requires a watchmaker. A Designer, whom Paley identified
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with God.
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It’s an argument worth considering. If you found a watch lying on
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the ground, you would indeed surmise that someone had designed it.
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And there are specific mechanisms inside our bodies that, for example, help
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us tell time. (Among them is a protein, cleverly named CLOCK, whose
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production plays a crucial role in regulating our daily circadian rhythm.)
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The human body is much more complex than a mechanical watch.
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Concluding that biological organisms are designed doesn’t seem like much
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of a leap.
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We might be cautious about where exactly we should be leaping. David
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Hume, in his Dialogues Concerning Natural Religion, argued fairly
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compellingly— and even before Paley had popularized the “watchmaker
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analogy” version of the argument from design— that there is a substantial
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difference between “a designer” and our traditional notion of God. Paley’s
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argument nevertheless has a good deal of persuasive power, and continues
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to be popular today.
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Immanuel Kant, writing in 1784, mused, “There will never be a Newton
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for the blade of grass.” Sure, you can invent unbending mechanistic rules
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governing the motions of planets and pendulums, but to account for the
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living world, you need to go beyond mindless patterns. There must be some-
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thing that accounts for the purposive nature of living creatures.
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These days we know better. We even know who the Newton for the
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blade of grass turned out to be: his name was Charles Darwin. In 1859,
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Darwin published On the Origin of Species by Means of Natural Selection,
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in which he laid out the basis for the modern theory of evolution. The great
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triumph of Darwin’s theory was not only to account for the history of life
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as revealed in the fossil record, but to do so without invoking any kind of
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purpose or external guidance—“design without a designer,” as biologist
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Francisco Ayala has labeled it.
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Essentially every working professional biologist accepts the basic expla-
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nation provided by Darwin for the existence of complex structures in bio-
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logical organisms. In the famous words of Theodosius Dobzhansky,
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“Nothing in biology makes sense except in the light of evolution.” But evo-
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lution happens within a larger context. Darwin takes as his starting point
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creatures that can survive, reproduce, and randomly evolve, and then shows
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how natural selection can act on those random changes to produce the il-
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lusion of design. So where did those creatures come from in the first place?
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Our goal over the next few chapters is to address the origin of complex
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structures— including, but not limited to, living creatures— in the context
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of the big picture. The universe is a set of quantum fields obeying equations
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that don’t even distinguish between past and future, much less embody any
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long- term goals. How in the world did something as organized as a human
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being ever come to be?
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The short answer comes in two parts: entropy and emergence. Entropy
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provides an arrow of time; emergence gives us a way of talking about collec-
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tive structures that can live and evolve and have goals and desires. First we’ll
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focus on entropy.
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The role of entropy in the development of complexity seems counterin-
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tuitive at first. The second law of thermodynamics says that the entropy of
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isolated systems increases over time. Ludwig Boltzmann explained entropy
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to us: it’s a way of counting how many possible microscopic arrangements
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of the stuff in a system would look indistinguishable from a macroscopic
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point of view. If there are many ways to rearrange the particles in a system
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without changing its basic appearance, it’s high- entropy; if there are a rela-
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tively small number, it’s low- entropy. The Past Hypothesis says that our
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observable universe started in a very low- entropy state. From there, the
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second law is easy to see: as time goes on, the universe goes from being low-
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entropy to high- entropy, simply because there are more ways that entropy
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can be high.
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Increasing entropy isn’t incompatible with increasing complexity,
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but it can seem that way because of how we sometimes translate the techni-
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cal terms into informal speech. We say that entropy is “disorderliness” or
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“randomness,” and that it always increases in isolated systems (such as
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the universe). If the general tendency of stuff is to grow more random
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and disorganized, it might seem strange that highly organized subsys-
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tems come into being without any guiding force working behind the
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scenes.
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There’s a common response to this worry, which is perfectly correct but
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doesn’t quite get at the underlying concern. It goes like this: “The second
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law is a statement about the growth of entropy in isolated systems, ones that
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don’t interact with an external environment. In open systems, exchanging
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energy and information with the outside world, of course entropy can go
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down. The entropy of a bottle of wine goes down when you put it in a re-
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frigerator because its temperature goes down, and the entropy of your room
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goes down when you clean it up. None of that violates the laws of physics,
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since the total entropy is still going up— refrigerators expel heat from the
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back, and human beings sweat and grunt and radiate as they clean up a
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room.”
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While it addresses the letter of the concern, this response sidesteps
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its spirit. The emergence of complex structures on a place like the surface
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of the Earth is completely compatible with the second law, and it is silly
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to suggest otherwise. The Earth is an extremely open system, radiating
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into the universe and increasing its total entropy all the time. The prob-
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lem is, while that explains why organized systems can come into being
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here on Earth, it doesn’t explain why they actually do. A refrigerator low-
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ers the entropy of its contents, but only by making them colder, not by
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making them more intricate or complex. And rooms can be cleaned,
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but in our experience it seems to require exactly what Paley was talk-
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ing about: an external intelligence to do the work. Rooms don’t spontane-
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ously clean themselves, even if we allow them to interact with the
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environment.
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We still need to understand how and why the laws of physics brought
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about complex, adaptive, intelligent, responsive, evolving, caring creatures
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like you and me.
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What do we mean by “simple” or “complex,” and how do they relate to en-
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tropy? Intuitively, we associate complexity with low entropy, and simplicity
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with high entropy. After all, if entropy is “randomness” or “disorganiza-
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tion,” that sounds like the opposite of how we think about the intricate
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mechanisms we find in a wristwatch or an armadillo.
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Our intuition here is a bit off. Think of mixing cream into coffee, inside
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a glass mug. Since we’re doing a physics experiment rather than a morning
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ritual, let’s do it first by gently putting the cream on top of the coffee, and
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only then mixing them together with a spoon. (The spoon is an external
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influence, but not a guided or intelligent one.)
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At the beginning, the system is low- entropy. There are relatively few
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ways to rearrange the atoms in the cream and coffee without changing its
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macroscopic appearance; we could swap individual cream molecules
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amongst themselves, or individual molecules in the coffee, but once we
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started exchanging cream with coffee, our glass mug would look different.
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At the end, everything is mixed together and the entropy is relatively high.
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We could exchange any bit of the mixture with any other bit and the system
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would look essentially the same. Entropy has gone up throughout the pro-
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cess, just as the second law would lead us to expect.
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Mixing cream into coffee. The initial state is low- entropy and simple. The final state is 25
high- entropy and simple. The intermediate, medium- entropy state exhibits interesting 26
complexity.
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But it’s not true that complexity has gone down as entropy has gone up.
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Consider the first configuration, with cream and coffee totally separate; it’s
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low- entropy, but it’s also manifestly simple. Cream on top, coffee on bot-
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tom, nothing else going on. The final configuration, with everything mixed
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together, is also quite simple. It’s completely characterized by saying “every-
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thing is mixed together.” It’s the intermediate stage, in between low entropy
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and high entropy, where things look complex. Tendrils of cream reach into
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The cream- and- coffee system exhibits behavior that is very different
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from a naïve identification of “increasing entropy” with “decreasing com-
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plexity.” Entropy goes up, as the second law says it should; but complexity
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first goes up, then goes down.
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At least, that’s the way it looks. We haven’t yet given a precise definition
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of what we mean by “complexity,” as we were able to do for entropy. Partly
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that’s because there is no one definition that works for every circumstance—
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different systems can exhibit complexity in different ways. That’s a feature,
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not a bug; complexity comes in many forms. We can ask about the complex-