The question this note comes from is old and the answer people reach for is usually wrong. If determinism is true, if every decision is in principle knowable from what came before it, does it follow that the financial future is predictable? The paper argues that it does not, and that the failure is structural rather than a shortfall of data or computing power. More data does not close this gap, because the gap is not made of missing data.
It fails twice, at two different joints. The first is general: sensitive dependence on initial conditions, computational irreducibility, and the problem a predictor has predicting a system it is itself inside. The second is specific to markets: a forecast, once acted on, alters the thing it forecast; an informationally efficient market cannot exist, because nobody would pay to gather the information that made it efficient; and models shape the behaviour they claim to describe. None of this is mine. Assembled well it is a literature review, not a paper, and the note says so about itself.
What is left to claim comes from SIMEA. If agents are decision subjects steered by systems rather than autonomous optimisers, then how much of a behaviour is generated externally varies between agents, between markets and over time. Externally generated behaviour is by construction more forecastable, because it is a function of an input a modeller can in principle observe. That gives the first proposition: forecastability falls as the autonomy threshold rises and climbs as the influence gradient grows. Predictability stops being a property a market has or lacks and becomes a coordinate it sits at.
That reframes the original question rather than answering it yes or no. Predictability was never a consequence of determinism. It is a consequence of influence. A world can be fully deterministic and unforecastable, and a world can be indeterministic in its foundations and highly forecastable at the level where the steering happens. And there is a second proposition that will not leave the first alone: predictability produced by systemic influence is arbitraged away once it is identified, which pushes influence architectures to escalate, to steer harder in order to keep producing it.
The note is a positioning note and there is no draft yet, which is the accurate description of where it stands. It carries a section on what would sink the argument, written before anyone else could write it. And it carries the part I would want read first if only one section could be: the source check. Every reference was verified against a publisher or DOI level record, and ten needed correction. Then each source was checked for whether it actually says what the note claims it says. Six of twenty are done. Four of those claims held and two failed, both in the treatment of Popper and Samuelson, and both are corrected in the note. Everybody claims rigour. The part worth publishing is the audit that found two of your own claims false.