Have computer scientists proven the world is fundamentally unpredictable?

Question

In the book "This Will Make You Smarter: 150 New Scientific Concepts to Improve Your Thinking", Rudy Rucker, a computer scientist, state:

A little-known truth: Every aspect of the world is fundamentally unpredictable. Computer scientists have long since proved this.
How so? To predict an event is to know a shortcut for foreseeing the outcome. A simple counting argument shows that there aren't enough shortcuts to go around. Therefore most processes aren;t predictable. A deeper argument plays on the fact that if you could predict your actions, you could deliberately violate your predictions, which means the predictions were wrong after all.
We often suppose that unpredictability is caused by random inputs from higher spirits or from low-down quantum foam. But chaos theory and computer science tell us that non-random systems produce surprises on their own. The unexpected tornado, the cartoon safe that lands on Uncle George, the winning pull on a slot machine odd things pop out of a computation. The world can simultaneously be deterministic and unpredictable.

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My first question relates to references. Where can I read about computer scientists "proving" the world is "fundamentally unpredictable"?

Second, can someone elaborate on the argument? For instance, consider the phrase

if you could predict your actions, you could deliberately violate your predictions, which means the predictions were wrong after all.

This is just bad modelling. If human agency (mine) affects the world, then my model should incorporate my action. And thus, I can predict what my action would cause to the world. So I don't see how this argument holds.

I also don't understand how the world can be deterministic and unpredictable. Rather, what happens is that the world is so complex that it is, to us, given our current state of our knowledge, unpredictable. But this is epistemological unpredictability and not necessarily ontological unpredictability, which is what you would assume is the meaning of "the world is unpredictable". The author seems to not know this difference.

Can some one please explain?

Answer 1

You are correct - there are many logical gaps and over-simplifications in the passage that you quote. To unpick just some of them:

• "Every aspect of the world is fundamentally unpredictable. Computer scientists have long since proved this": Computer scientists prove things about computing systems and models of computing systems. Whether this tells us anything about the "real world" is debatable.

• "If you could predict your actions, you could deliberately violate your predictions": There are two counters to this argument. The first is that it assumes we have free will, which is not certain - perhaps we only think we have free will. What if the very act of trying to violate a prediction is itself predictable and actually fulfills the prediction ? The second counter is that even if we do have free will, this logical argument only means that we cannot predict our own actions. It does not rule out some other (more advanced ?) being predicting our actions.

• "Chaos theory and computer science tell us that non-random systems produce surprises on their own" : What chaos theory actually tells us is that there are deterministic systems in which any uncertainty in initial conditions increases exponentially, leading to an uncertain future state that is, in effect, spread evenly across the whole configuration space. So deterministic systems can be unpredictable in the sense that any finite amount of information about the initial state does not let us conclude anything useful about a future state. But these "chaotic" systems are based on a continuous space of possible states. Whether they are accurate or useful models of the "real world" is, once again, debatable.