◉ The Cave-Design Error: Reference Classes, Natural Mechanisms, and the Failure of Complexity-to-Designer Inference

Complexity alone cannot warrant a designer. The familiar move from watches, books, machines, or codes to caves, organisms, and cosmic structure changes the comparison class while preserving a correlation established inside an artifact-rich sample. That transfer is invalid as a universal deduction and evidentially weak unless the target feature is more expected under a specified agent hypothesis than under specified non-agent alternatives. Known cave formation, evolutionary accumulation, co-option, and constrained material processes show why intricacy is not exclusive to agency. They do not prove that no designer exists; they raise the probability of complex outcomes under live non-agent pathways and thereby remove the shortcut. The paper reconstructs the cave analogy around four requirements: representative comparison classes, explicit causal alternatives, discriminating traces, and exposure to contrary evidence. It then tests stronger proposals. Specified complexity and irreducible complexity improve on mere wonder because they attempt to define a narrower target, but they still require justified probability models, independent specifications, and serious comparison with evolutionary pathways. Fine-tuning arguments are a different family and are not refuted by the cave analogy, though they face their own comparative burdens. Archaeology and forensics show what successful agency inference looks like: investigators use contextual traces, production sequences, causal access, and rival models rather than complexity alone. The conclusion is methodological and bounded. Complexity may identify a question worth investigating; only comparative trace evidence can identify agency.