The theologian Hugo Rahner argued that the homo ludens is a man of ‘Ernstheiterkeit’ (seriouscheerfulness), a person who can smile under tears but also recognizes the gravity in all earthly cheerfulness. The primary aim of this study was to test the validity of this notion: Do homines ludentes exist? Two hundred sixty-three adult subjects were measured for (1) seriousness and cheerfulness and (2) playfulness. Results provided unequivocal support for Rahner’s thesis. Numerous subjects scored high in both seriousness and cheerfulness thus confirming the existence of homines ludentes. It was further found that these subjects were among those scoring highest in playfulness. Subjects scoring high in cheerfulness but low in seriousness were, however, even more closely associated with playfulness. The scores for homines ludentes did not differ from the rest of the subjects in the creative and dynamic facets of playfulness. The importance of developing empirical research to investigate hypotheses derived from non-scientific concepts is discussed.