Actually chaos theory is ultimately inadequate to explain the markets, although its a better model than coin-tossing randomness. Chaos occurs in systems with nonlinear feedback -- in particular systems with positive feedback that cause amplification of small perturbations of the system. A chaotic system (in the scientific/mathematical sense) can be 100% deterministic with no random components, noise, etc. For example, one of the simplest deterministic chaotic systems is three (or more) bodies orbiting each other under gravitational influence. This simple system has no analytic solution and the motion cannot be reliably predicted for very long. And yes, this means, that the future motion of our solar system is ultimately NOT predictable in the long-run (IIRC, the current prediction limit is only few million years into the future). For a chaotic system, doubling the quantity/quality of data about the system only adds a small amount of additional predictive power -- its a serious case of diminishing returns.
<b>Controlling Chaotic Systems</b> Chaotic systems actually have some paradoxical features -- they may be unpredictable, but they can be extremely controllable. If you understand a chaotic system, you can actually control it with amazing accuracy and very little effort. If you know that a small perturbation amplifies to drive the system in a certain direction, then you can easily control the system with small inputs. Even more paradoxically, you don't even need to know the parameters of the system very accurately in order to control it. Applications include stabilizing the output of high-power lasers, enhancing the maneuverability of high-performance aircraft, and advanced heart pacemakers. If you don't believe me on this one, go out and start reading the academic literature on this topic. Perhaps the market analog of this is the games that MM and specialists play to blow-out people's stops or pump-n-dump shares. If the market were only chaotic, then a clever trader could become the boss of the market.
<b> The problem is that the markets are WORSE than chaotic.</b> To understand this fact, we need to understand an important fact about the vast majority of chaotic systems that most people study. Chaotic systems may be ultimately unpredictable in the behavior, they are consistent in behavior. This consistent pattern of behavior is called the "strange attractor" of the system. The reason for the consistency of behavior is that the chaotic systems studied by chaos systems theorists have a fixed, unchanging set of equations that define the behavior (gravity in a 3-body problem is the same yesterday, today, and tomorrow. The physical properties of air, water, and land that drive the weather are the same yesterday, today, and tomorrow).
<b>The changing physics of the markets</b> Where standard chaotic systems are driven by the inevitable and unchanging physics of their components (with nonlinear positive feedback loops that create chaos), the markets have a self-modifying, anticipatory element that causes the equations of motion to change over time. Its the old "traders know that other traders behave with fear and greed" so that means that "traders know that traders know that other traders behave with fear and greed"..... Traders are constantly seeking new patterns and by trading those patterns, they change the patterns. Moreover, the market structure can change as different types of trading and investing styles arrive or depart (for example trades that exploit the realignment of a stock index only work because of the current fad of stock index mutual funds). Finally, market clearing mechanisms, new markets, and regulatory changes impact the "equations of motion" of the markets (the list includes decimalization, SuperSOES, the rise of ECNs, the advent of extended hours trading, index ETFs, SSFs, etc.).
<b>Humans are sufficient, but not necessary for complex behavior:</b> Although the psychological and cognitive features of humans play a major role in how markets behave, a market with nonhuman participants can also display self-modifying complex behavior. It's not humans, per se, that make the market's behave in such a complex fashion. Instead any distributed system that consists of a myriad of interacting elements can display arbitrarily complex behavior (see "A New Kind of Science" by Wolfram, or look into the Artificial Life literature for how simple interactions among dumb, emotionless objects can beget strange behavior). Even market systems that only contain negative feedback loops can be unstable if lags in the information flow interact poorly with sensitive, high-speed feedback loops (go read basic control theory to understand this one).
<b>Chaos theory, better than the coin toss model, but still abysmal:</b> The people that caution about reading too much into chaos theory are right. Its an OK model for thinking about some aspects of market behavior, but, ultimately, its predictive power is low. (Likewise, I'd be very careful with all the 50:50 coin toss analogies that get "tossed" about on ET. The market is NOT a coin, market events are NOT independent, and you have no guarantee that 50:50 behavior in the past will mean 50:50 behavior in the future.)
Wishing that the markets actually were chaotic, cuz then I'd be the boss,
Traden4Alpha