Paradox of Predictability I think I understand your objection now. You are saying that a prediction of a prediction is necessary for the computer to printout anything intelligible about what Ned will or will not do.
Maybe you can see where I am coming from too? It seems to me that with sufficient information about the state of the world at time t1, one should be able to make an accurate prediction about how the world would be at time t2. What seems to matter is mapping information about where each atom is, neural activity, electrical activity, etc., such that a prediction at time T2 is possible. If determinism is true, the subjective state of someone "I am a counterpredictor in such and such situation" should not matter. In other words, what someone reads on a printout should not affect their behavior if we have already a complete map of their behavior in terms of atoms etc. So I agree with you that a counterpredictor can always act otherwise, but that seems to pose a contradiction for determinism; namely, that the prediction and counterprediction must both obtain.
It feels intuitively to me that in some, many, most? cases unraveling cause is not possible even in theory. It's not just a case of being ignorant. Part of that feeling is a conviction that sufficiently complex systems, even those that are theoretically "caused," could not be unraveled with the fastest supercomputer operating for the life of the universe. There is a point, isn't there, where "completely outside the scope of human possibility" turns into "not possible even in theory." Seems to me there is. — T Clark
The problem of computability described by T Clark seems to me to be a salient one. If the prediction cannot be made because of instrumentation that is not precise enough, or because there is just too much information for a supercomputer to process, then the prediction just cannot be made.
it could be that predictability is not achievable under the specified conditions.
The first paper that you cited makes an important point about predictability right in the abstract, by drawing a distinction between external predictability and embedded predictability: — SophistiCat
At first glance, it appears that determinism should imply predictability, if not in an embedded way, at least in an external way. The paper cited says about as much, although I am unclear as to why an embedded predictor cannot make a true and accurate prediction in a deterministic universe. Or at least, it is unclear to me why an external predictor cannot be physical. Seems as though an external predictor could be physical, and yet still external to the situation (e.g. a computer that does not share its predictions with the system or person that it is predicting about).
thanks everyone for commenting