p.468 in "A Neglected Argument" Peirce introduces the concept of "musement." This mode of thinking, while strikingly receptive and leisurely, is crucial to the strength of the Neglected Argument. Peirce explains musement as an activity which is "Pure Play." It is "a lively exercise of one's powers" and yet "has no rules, except this very law of liberty" (6.458). Though musement is leisurely in that it allows the muser to assume different standpoints, it also involves deliberate observation and meditation. "It begins passively enough with drinking in the impression of some nook in one of the three universes. But impression soon passes into attentive observation, observation into musing, musing into a lively give-and-take between self and self" (6.459). [JLJ - continues: If one's observations and reflections are allowed to specialize themselves too much, the Play will be converted into scientific study] While in a sense passive and receptive, musement is also that in which "logical analysis can be put to its full efficiency" (6.461). We might say that, while "musing," one is both "active" and "contemplative," and that this active receptivity somehow contributes to the reliability of the Neglected Argument.

p.468 an examination of Peirce's early studies of aesthetics (between 1855 and 1857) shows that the notion of musement likely has its provenance in his reading of Friedrich von Schiller, and that Schiller considered musement or leisurely thinking to be the highest realization of human intellectual powers.

p.469 Of importance for the present discussion, however, is Schiller's notion of the "play impulse" that makes possible a balance between the "material" and "spiritual" (what he also calls "passive" and "active") aspects of humanity... Through the "play impulse," he answers, the two human capacities temper each other, and one is able to apprehend beauty, which is the proper object of play. In answer to the possible objection that his view makes the concept of beauty subject to frivolity, a mere "game," he states: "But why call it a mere game, when we consider that in every condition of humanity it is precisely play, and play alone, that makes man complete and displays at once his twofold nature?" For man's freedom "consists solely in the co-operation of both his natures." Schiller later iterates this thought when claiming that man "plays only when he is in the full sense of the word a man, and he is only wholly Man when he is playing."

p.469 Peirce was considering cognitive "play" in inferential terms, and as something contributing to the security of an argument or argumentation, since it involves the highest exercise of human powers.

p.470 The state of musement provides a context in which the muser may leisurely appreciate some "wonder," and in which the hypothesis accrues a spectacular momentum necessary for the persistent determination of the will.

p.471 according to Peirce, musement exercises that which is properly human. That is, only humans are capable, he suggests, of engaging in non-purposive, impractical thinking which is nonetheless supremely active. Musement, though leisurely and in that sense "liberal" or free, is at the same time abuzz with suggestions of "rules" drawn from past experience and from what is possible but not yet experienced; in this activity the mind, freely and informally, traces the ramifications of countless hypotheses, ultimately fixing on a "smoothly fitting key."

p.471 it seems that musement... describes the cognitive process that transpires in abductive inference generally, which process is the source of ingenuity.