We have included materials aging here as an example of a deductive problem resulting from hidden information. This limitation is intrinsic, because the detailed history of any material can never be completely specified. Nevertheless, there are deductive constraints that are potentially inexpensive that could make prediction possible. Returning to the adhesive example, although the specific history might be unknown, analyzing the current water content of the material might constrain the range of possible behaviors. In such cases, a model might be predictive for some functional property that is presumably difficult to measure in situ, if supplied some external information that could narrow the range of histories. Such deductive reasoning is intuitive to an expert, but not currently considered in the design of contemporary ML models.