Philosophers of history have posited a class of concepts known as colligatory concepts (CCs) that causally link a series of past events into a meaningful pattern that is evaluated as significant for historical knowledge and that contributes to historical consciousness. We tested the hypothesis that these colligatory concepts occurred frequently in dreams and nightmares relative to waking narratives and that they exhibited properties that plausibly allowed them to mediate historical consciousness. In our content analysis of 100 nightmares, 100 unpleasant control dream narratives, and 50 waking narratives (diary entries), colligatory concepts appeared in 75% of nightmares and 46% of ordinary dreams compared to 2% of diary entries. In 36 out of 75 (48%) nightmares, 13 out of 46 (28.3%) unpleasant dreams, and 0 out of 1 diary entries the causal reference invoked by the CCs referred to group or social collective effects of some kind. In slightly more than half (56%) of the nightmares, 7% of unpleasant dreams, and 0% of diary entries containing CCs, the evaluative emotion was fear or terror. Colligatory concepts occur frequently in nightmares and dreams and most often refer causes of events in dreams to group or collective effects that are experienced as terrifying or disturbing.