Dementia Is Not Forgetting: Distinguishing Compression Function Collapse from Healthy Verbatim Decay

f forgetting is compression (Murata, 2026r), then dementia should be beneficial. It is not. This apparent contradiction is the strongest objection to the forgetting axiom, and this paper resolves it. Healthy forgetting is the decay of verbatim representations while gist representations are preserved and strengthened—the compression function operating normally. Dementia is the progressive collapse of the compression function itself: gist representations degrade, structural understanding dissolves, and eventually the individual cannot compress even immediate experience into meaning. The distinction between healthy forgetting (verbatim loss, gist gain) and pathological forgetting (gist loss, function collapse) is the sharpest diagnostic prediction ACAT produces: it implies that early dementia should be detectable not by measuring what patients forget (verbatim), but by measuring what they can no longer compress (gist extraction from novel inputs). Five predictions for early detection and intervention are provided.