Intelligibility of nearest-neighbor classifiers is a complex issue. As mentioned, in some fields such as medicine and law, reasoning about similar historical cases is a natural way of coming to a decision about a new case. In such fields, a nearest-neighbor method may be a good fit. In other areas, the lack of an explicit, interpretable model may pose a problem. There are really two aspects to this issue of intelligibility: the justification of a specific decision and the intelligibility of an entire model.
