Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 Musement: the activity of the brain’s default mode network Antonio Duarte Dept. Logic and Theoretical Philosophy Universidad Complutense de Madrid Abstract: The main purpose of this article is to identify the inner human activity Peirce calls musement with the mental processes that arise through the workings of the brain’s default mode network. This network is a specific, recently anatomically defined brain system, which is most active when individuals are not focused on the external environment. In doing so, musement, which was defined by Peirce over a hundred years ago, will finally be situated within what today we understand as its neurobiological origin. Keywords: abduction, default mode network, musement, Peirce 1. Introduction “Semiotics begins and ends with biology and the sign science and the life science ineluctably imply each other.” (Sebeok 1979: viii) In 1908, Peirce introduced his notion of musement in The Neglected Argument of the Reality of God as “a non-reflective mental activity, capable of giving a sort of instinctive response to produce a strong belief in the reality of God” (Rodrigues 2017: 164). That capability is possible because musement involves abduction, which is the way humans attain strong beliefs. This paper retraces Peirce’s discussion of musement “as at once a consideration of abduction and of the imagination’s role in it” (Anderson 2005: 17), i.e. musement as a “certain agreeable occupation of mind” (Peirce, CP 6.458, 1908) capable of originating new ideas. Nevertheless, the main goal of this work is to connect Peirce’s description of musement to the novel concept of the brain’s default mode network (DMN). Over the last decade, neuroscientists have defined and demarcated the brain’s DMN, a brain system which has only recently come to be appreciated and which participates in internal modes of cognition (Buckner et al. 2008). Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 2. What is musement? Musement is a specific type of mental activity, but, as Peirce states, it is one that has no distinctive name (Peirce, CP 6.458, 1908). It also seems rather difficult to describe it in a precise and unambiguous way. As I mention in the Introduction, for Peirce, musement could lead to ideas concerning the “reality of God”; but it is not this idea or result which characterizes musement. The thought process of musement tends to produce beliefs in a broad sense (see e.g. Caleb Clanton 2014), but in a rather peculiar state of the mind. Peirce based his notion of musement on Schiller’s aesthetic concept of Spieltrieb1 (see e.g. Sebeok 1981; Chiasson 2001; Peirce, SS 77, 1908), a drive towards free play: “the aesthetic tendency, mediating and harmoniously reconciling the twofold way of sense and reason on the level of the individual’s faculties (microcosmos, the particular) as well as those of society (macrocosmos, the lofty)” (Sebeok 1981: 1). In The Neglected Argument of the Reality of God, Peirce encompasses within musement this aesthetic attitude, free play, together with “a heuristic device for explaining the way in which new possibilities are discovered and explored” (Chiasson 2001: 7). Nonetheless, I think that for every single human being, the easiest way to recognize what musement is and to fully identify it as a unique mental process that our minds engage in, is to follow Peirce’s description of it. So I will proceed step by step, and initially, in what follows, underline the essential characteristics of musement. [1]. Musement is an agreeable occupation of mind without a distinctive name: There is a certain agreeable occupation of mind which, from its having no distinctive name, I infer is not as commonly practiced as it deserves to be. (Peirce, CP 6.458, 1908) [2]. Musement is occupation of mind without purpose but different from reverie: Because it involves no purpose save that of casting aside all serious purpose, I have sometimes been half-inclined to call it reverie with some qualification; but for a frame of mind so antipodal to vacancy and dreaminess such a designation would be too excruciating a misfit. (Peirce, CP 6.458, 1908) [3]. Musement is pure play of mind with no rules: In fact, it is Pure Play. Now, Play, we all know, is a lively exercise of one's powers. Pure Play has no rules, except this very law of liberty. It bloweth where it listeth. It has no purpose, unless recreation. (Peirce, CP 6.458, 1908) [4]. Musement connects universes: The particular occupation I mean [...] may take either the form of aesthetic contemplation, or that of distant castle- building (whether in Spain or within one's own moral training), or that of considering some wonder in one of the Universes, or some connection between two of the three, with speculation concerning its cause. It is this last kind – I will call it "Musement" on the whole– that I particularly recommend. (Peirce, CP 6.458, 1908) 1 Friedrich Schiller, On the aesthetic education of man, 1794, especially Letters XVIV, XVV. Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 [5]. Musement can begin at any time, passively: The dawn and the gloaming most invite one to Musement; but I have found no watch of the nychthemeron that has not its own advantages for the pursuit. It begins passively enough with drinking in the impression of some nook in one of the three Universes. (Peirce, CP 6.459, 1908) [6]. Musement can be converted into scientific study: But impression soon passes into attentive observation, observation into musing, musing into a lively give and take of communion between self and self. If one's observations and reflections are allowed to specialize themselves too much, the Play will be converted into scientific study; and that cannot be pursued in odd half hours. (Peirce, CP 6.459, 1908) [7]. Musement can help to solve problems: Since, then, it is certain that man is able to understand the laws and the causes of some phenomena, it is reasonable to assume, in regard to any given problem, that it would get rightly solved by man, if a sufficiency of time and attention were devoted to it. Moreover, those problems that at first blush appear utterly insoluble receive, in that very circumstance, as Edgar Poe remarked in his "The Murders in the Rue Morgue," ["It appears to me that this mystery is considered insoluble for the very reason which should cause it to be regarded as easy of solution. I mean the outré character of its features"] their smoothly-fitting keys. This particularly adapts them to the Play of Musement. (Peirce, CP 6.460, 1908) [8]. Musement encompasses all kinds of reasoning: Forty or fifty minutes of vigorous and unslackened analytic thought bestowed upon one of them usually suffices to educe from it all there is to educe, its general solution. There is no kind of reasoning that I should wish to discourage in Musement; and I should lament to find anybody confining it to a method of such moderate fertility as logical analysis. (Peirce, CP 6.461, 1908) [9]. Musement is broader than a single method of logic or scientific study: Only, the Player should bear in mind that the higher weapons in the arsenal of thought are not playthings but edgetools. In any mere Play they can be used by way of exercise alone; while logical analysis can be put to its full efficiency in Musement. (Peirce, CP 6.461, 1908) [10]. Musement is an inner dialogue of ideas and images: So, continuing the counsels that had been asked of me, I should say, "Enter your skiff of Musement, push off into the lake of thought, and leave the breath of heaven to swell your sail. With your eyes open, awake to what is about or within you, and open conversation with yourself; for such is all meditation." It is, however, not a conversation in words alone, but is illustrated, like a lecture, with diagrams and with experiments. (Peirce, CP 6.461, 1908) [11]. Musement is open to take different courses: Different people have such wonderfully different ways of thinking that it would be far beyond my competence to say what courses Musements might not take. (Peirce, CP 6.462, 1908) [12]. Musement can provide plausible suggestions that need further testing: At this point [...] a trained mind will demand that an examination be made of the truth of the interpretation; and the first step in such examination must be a logical analysis of the theory. But strict examination would be a task a little too serious for the Musement of hour fractions, and if it is postponed there will be ample remuneration even Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 in the suggestions that there is not time to examine; especially since a few of them will appeal to reason as all but certain. (Peirce, CP 6.464, 1908) Musement, as pure play, is not a hard mental task. Pure play begins passively in those moments when the mind is free of limits, unbiased, and unfocused. Caleb Clanton (2014) points out that: in order to engage in pure play, the mind must (a) achieve a certain degree of vacancy at the outset and (b) have no antecedent purpose or aim in view other than (a) a recreational “scientific singleness of heart” [...] (d) as it candidly employs the “lively exercise of one’s powers” while (e) observing no rules other than the “law of liberty”. (Caleb Clanton 2014: 177) So, naively, pure play may connect in any way the three Universes of Experience (of Ideas, of Brute Actuality, and of Signs [Peirce, CP 6.455, 1908]) and become a specific sort of pure play: musement. This is different from reverie because, although distantly and in an unserious way, musement spins around our experience of life: “reflection on, and speculation about the cause of, either some surprising phenomenon within one of the three universes of experience or some surprising connection between two or three of the universes” (Caleb Clanton 2014: 177-178). In musement, the mind naturally imagines a range of hypotheses, action possibilities or explanations, depending on the pathway one’s thoughts freely take. Moving on to the more creative side of this mental activity, many times, while playfully engaged in musement, we “spontaneously” encounter the key idea that will solve an enigma that occupied our mind in moments when we were focused on a specific task. Connecting to Peirce’s theory of abduction, after this suggestion that appears to us during musement, further testing is needed to verify the plausible hypothesis. In this way, musement can be seen as closely connected to abduction and creativity. Wirth (2014: 6) summarizes musement as “a mental movement oscillating between freedom and the reoccupation of the mind by the constraints of self-control” and also points out that: “abductive and conjectural thinking is in the beginning ‘pure Play’, which is not controlled by critical reason. [...] The result of Musement can be a creative, witty Abduction. [...]. Abduction is, ‘the idea of putting together what we had never before dreamed of putting together (an idea) which flashes the new suggestion before our contemplation’ (CP 5.181).” Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 3. How do we play at musement? Musement can begin at any time, passively. Discussing Musement, Barrena (2008) cites a passage written by Peirce where he explains his idea about the action of thought, which is excited by the irritation of doubt, and ceases when belief is attained. Most frequently doubts arise from some indecision, however momentary, in our action. Sometimes it is not so. I have, for example, to wait in a railway-station, and to pass the time I read the advertisements on the walls. I compare the advantages of different trains and different routes which I never expect to take, merely fancying myself to be in a state of hesitancy, because I am bored with having nothing to trouble me. Feigned hesitancy, whether feigned for mere amusement or with a lofty purpose, plays a great part in the production of scientific inquiry. However the doubt may originate, it stimulates the mind to an activity which may be slight or energetic, calm or turbulent. Images pass rapidly through consciousness, one incessantly melting into another, until at last, when all is over – it may be in a fraction of a second, in an hour, or after long years – we find ourselves decided as to how we should act under such circumstances as those which occasioned our hesitation. In other words, we have attained belief. (Peirce, CP 5.394, 1893) In this text, as we see, Peirce’s mind begins to engage in play passively. At first, he is nonchalantly reading the advertisements on the walls; but this soon passes into attentive observation (“I compare the advantages of different trains and different routes”), observation into musing (“fancying myself to be in a state of hesitancy”), and then “musing into a lively give and take of communion between self and self” (“images pass rapidly through consciousness, one incessantly melting into another”). Peirce, therefore, is practicing the pure play of musement. As Barrena (2008: 34) points out: “Imagination games, the freeing of the mind, could be especially fertile when it comes to acquiring habits or attaining beliefs that will help our knowledge and orientation in reality. Through imagining, playing in our mind, we can change the way we face reality; reacting to situations that we had imagined at some time and that later on become real.” (My own translation from the original Spanish)2. In this sense, this play of musement is also closely connected to Peirce’s concept of a virtual habit (see West 2016). In the processes of generating an ongoing event picture in our mind, or of representing within our thoughts episodes in the future, virtual habits (i.e. virtual attained beliefs) determine which newly conceived hypotheses are more viable or will produce a particular outcome. Therefore, musement, as free play of the mind, spins around our experience of life: it is a “natural” or “unconscious” method which tracks early decision-making. Additionally, in the pure play of musement, there is also a relationship between strenuous focused mental activities and more mundane practices. Sebeok (1981: 35) illustrates this point via a 2 Los juegos de la imaginación, el dejar libre la mente, pueden mostrarse especialmente fecundos a la hora de adquirir hábitos o de fijar creencias que ayudarán a nuestro conocimiento y a nuestra orientación en la realidad. Imaginando, jugando en nuestra mente, podemos llegar a cambiar nuestra manera de enfrentarnos a la realidad, de reaccionar ante situaciones que habíamos imaginado en algún momento y que más adelante llegan a volverse reales. (Barrena 2008: 34) Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 well-known peculiarity of Sherlock Holmes’ personality: “Holmes was known to oscillate between the almost frenzied singlemindedness of the fox-hound on the trail of his quarry and a sort of lethargic reverie.” Moreover, quoting Holmes’s sidekick, Watson, Sebeok further points out that the latter type of activity was also important to Holmes’s detection (Sebeok 1981: 35). Therefore, Holmes plays at musement when he immerses himself in the music that he recreates with his violin; as Watson points out on many occasions, Holmes rather surprisingly usually does so in the middle of an important investigation: “long into the watches of the night I heard the low, melancholy wailings of his violin, and knew that he was still pondering over the strange problem which he had set himself to unravel.” (Doyle 2018 [1887]) It is also through pure play that Einstein solves some of the most intricate problems facing him, pursuing the very same method. Isaacson (2007: 14) points this out by quoting the words of Einstein’s son, Hans Albert: “Whenever he felt that he had come to the end of the road or faced a difficult challenge in his work,” said his son Hans Albert, “he would take refuge in music and that would solve all his difficulties.” The violin thus proved useful during the years he lived alone in Berlin, wrestling with general relativity. “He would often play his violin in his kitchen late at night, improvising melodies while he pondered complicated problems,” a friend recalled. “Then, suddenly, in the middle of playing, he would announce excitedly, ‘I’ve got it!’ As if by inspiration, the answer to the problem would have come to him in the midst of music.” (Isaacson 2007: 14) Interestingly, playing an instrument requires the use of procedural memory, which is usually accessed without the need for conscious control or attention. Therefore, it is a kind of activity that helps us to disengage from the external environment and allows the mind to wander freely. Then, after the breakthrough of insight, further testing of the hypothesis is needed, but playful musement is how, many times, the mind solves those problems that at first blush appear utterly insoluble (no doubt Holmes’s and Einstein’s problems would initially appear utterly insoluble). Thus, musement often helps in the process of arriving at the new hypothesis: “the abductive suggestion comes to us like a flash” (Peirce, CP 5.181, 1903). Therefore, thanks to the connections between the universes made by musement, we illuminate a new idea that, in a few seconds, may be a hypothesis. Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 4. The brain’s default mode network “When the brain/mind thinks in a free and unencumbered fashion, it uses its most human and complex parts.” (Andreasen et al. 1995: 1583) This section is devoted to presenting the DMN, a brain system recently discovered by neuroscientists, and its connection to creativity. To give a concise though rigorous overview of the DMN here, I mostly base my offering on the works of Buckner et al. (2008), Buckner (2013), and Beaty et al. (2014). The DMN is a specific, anatomically defined brain system that becomes activated when subjects are not focused on the external environment: when no externally directed task is in progress. The network has been shown to consistently decrease its activation when an external task is presented, and to increase in the absence of the demands of an external task. Nonetheless, this brain system is also active when individuals are engaged in directed but internally focused tasks, including autobiographical memory retrieval, envisioning the future, and conceiving the perspectives of others. Interestingly, the DMN operates in opposition to other brain systems that are used for focused external attention and sensory processing: when the DMN is most active, the external attention system is attenuated, and vice versa. This finding suggests that the brain may shift between two distinct modes of information processing that represent functionally competing brain systems. Evidence of the DMN began accumulating when researchers measured brain activity in people during undirected mental states. Although the early studies were not explicitly designed to explore such unconstrained states, the relevant data were acquired because of the common practice of using rest or other types of passive conditions as an experimental control. In early work, Andreasen et al. (1995) observed that during passive tasks, the DMN showed activation in regions that were also active when individuals recalled information from their episodic memory. The experimenters noted that the resting state “is in fact quite vigorous and consists of a mixture of freely wandering past recollection, future plans, and other personal thoughts and experiences.” (Andreasen et al. 1995: 1578) They also noted that the regions involved were “more highly developed (i.e., comprise a larger portion of the brain volume) in human beings than in nonhuman primates or other animals” (Andreasen et al. 1995: 1583). A series of publications by Raichle, Gusnard, and colleagues (Raichle et al. 2001; Gusnard & Raichle 2001; Gusnard et al. 2001) brought exploration of the DMN to the fore as its own area of study. Their work made it clear that the DMN is a fundamental neurobiological system with physiological and cognitive properties that distinguish it from other systems. Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 Self-reported data from neuroimaging tasks that activate the DMN reveal that mind wandering and spontaneous thoughts occur frequently. The network is best understood as multiple interacting subsystems; and the possibility that the DMN contributes to internal channels of thought is consistent with the subsystems that comprise its anatomy. The medial temporal lobe subsystem provides information from prior experiences. The medial prefrontal subsystem facilitates the flexible use of this information during the construction of self-relevant mental simulations. These two subsystems converge on important nodes of integration including the posterior cingulate cortex. When quizzed, participants in experiments probing the DMN report a wide range of mental phenomena, including episodic future thinking, mental simulation, perspective taking, and mind wandering. One working hypothesis is that the primary function of the DMN is to support internal mental simulations (internal mentation) that are used adaptively. The adaptive function may be to provide a “life simulator” (Gilbert & Wilson 2007). Such imagined events tend to be practical and free from fantasy-like qualities. According to this hypothesis, a defining property of the DMN is its flexibility. The tasks (i.e. remembering, envisioning the future, conceiving the mental states of others…) that activate the DMN share core processes but differ in terms of content and the goal to which the processes are applied. Knowledge that the default network exists reminds us that there may be specialized brain systems that underlie our abilities to mentally explore and anticipate future situations. Such constructive processes may be adaptive because they allow the brain to preexperience upcoming events and to derive prospectively useful forms of representation that are many steps removed from their originally encoded sources. [...] The default network’s prominent use during passive epochs may contribute adaptive function by allowing event scenarios to be constructed, replayed, and explored to enrich the remnants of past events in order to derive expectations about the future. This functional role may explain why the default network increases its activity during passive moments when the demands for processing external information are minimal. Rather than let the moments pass with idle brain activity, we capitalize on them to consolidate past experience in ways that are adaptive for our future needs. (Buckner et al. 2008: 31) Neuroscience has been much applied to the study creativity in the recent years, by means of experiments involving divergent thinking: a central component of general creative ability (see Beaty et al. 2014 and references therein). These works point to important roles of different brain areas: the inferior prefrontal cortex, associated with controlled memory retrieval and central executive processes, and the DMN, associated, as we have seen above, with internally-directed attention and spontaneous cognition. Beaty et al. (2014) analyzed resting-state functional connectivity in participants of both high and low divergent thinking ability, to address the potential role of the DMN in creative thought. Participants were prescreened via a battery of divergent thinking tests and assigned to high and low creativity groups. Then, they completed a series of divergent thinking tasks in the lab and subsequently Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 underwent resting-state functional imaging. Seed-based functional connectivity analysis revealed greater connectivity between the left inferior frontal gyrus and the entire DMN in the high creativity group. The results suggest that the ability to generate creative ideas is characterized by increased functional connectivity between the inferior prefrontal cortex and the DMN, indicating greater cooperation between brain regions associated with controlled and spontaneous cognitive processes. Studies of other abilities involving creativity also point to the important role of the DMN. Ellamil et al. (2012) found differential contributions from executive control and the DMN during different stages of a creative drawing process: regions of the DMN were more strongly activated during idea generation, and regions of the executive control network were more strongly activated during idea evaluation. As I hope to have made clear, the DMN supports mental simulations and is also closely connected to creativity. Hence, we may conclude that the DMN is the responsible for certain types of mental activity that characterize human beings and distinguish humans from other animals. 5. The activity of the brain’s default mode network “Just as for [...] thousands of men a falling apple was nothing but a falling apple; and to compare it to the moon would by them be deemed ‘fanciful’.” (Peirce, CP 1.46, 1896) The discovery of the DMN offers a new approach to the analysis of the effects of new technologies and multitasking environments on our brains. One of the most beautiful examples is the allegation made by Smart (2013) defending being idle and the important role of the activity of the DMN for human beings. Smart dedicates a passage of his book to telling the story of Newton and the falling apple, one of the most famous anecdotes in the history of science, from a neurobiological perspective. This passage illustrates how the DMN works and the results of such brain activity. The truth of the tale of the apple is supported by the William Stukeley’s (1752) biography of Newton, entitled Memoirs of Sir Isaac Newton's Life: After dinner, the weather being warm, we went into the garden, and drank thea under the shade of some appletrees, only he, and myself. Amidst other discourse, he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. "Why should that apple always descend perpendicularly to the ground," thought he to him self: occasion'd by the fall of an apple, as he sat in a comtemplative mood: "why should it not go sideways, or upwards? But constantly to the earths centre? Assuredly, the reason is, that the earth Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 draws it. There must be a drawing power in matter. And the sum of the drawing power in the matter of the earth must be in the earths center, not in any side of the earth. Therefore this apple fall perpendicularly, or toward the center. If matter thus draws matter; it must be in proportion of its quantity. Therefore the apple draws the earth, as well as the earth draws the apple. (Stukeley 1752) Even if the tale is fruit of the fanciful imaginings of Newton or of his biographer, this story is representative of the way in which eureka moments appear. Nonetheless, the passage seems realistic insofar as there are several features of Stukeley’s account that fit the properties of musement and of the DMN: the contemplative mood, the mind wandering around the question of why an apple falls in a peculiar way, and the insight, the great idea concerning the power in the matter of the earth. That idea was enough to connect apparently independent phenomena. If there is a power in the matter of the earth, that power may produce effects on both small nearby objects (an apple) and large distant ones (the moon). Obviously, a great imagination, solid background knowledge and, very importantly, a previously unresolved problem in mind are necessary for the brain’s DMN to make such amazing connections. Smart (2013), meanwhile, describes the activity of Newton’s DMN during the apple falling incident in the following way: He would have had a feeling of well-being and sensations of positive emotions might have washed over him. All this would put him in a nice “contemplative mood.” His default mode network would have started to increase its activity. Blood would have started flowing to his precuneous, his lateral parietal cortex, his medial prefrontal cortex, and his anterior cingulate cortex as these regions began to consume oxygen and glucose at an increased rate. This is the default mode network getting warmed up. The neurons in these regions are increasing their activity. His anterior cingulate would have signaled to his parasympathetic nervous system that all was well and his blood pressure would drop. His heart rate would slow and time between beats would start to become slightly more variable. This physiological reaction would start to feed back to his brain and his relaxation might deepen. In this idle state and in the absence of some externally induced task, Newton’s brain starts to get to work. His mind begins to wander; his thoughts turn inward and become reflective. The nodes in his default mode network are now ready to communicate. […] Memories and associations, along with mathematical and spatial concepts, which are stored in regions connected to the parietal cortex, can also be accessed by his default mode network. [...] These reports from Newton’s vast knowledge of physics in his long-term memory, which are normally not part of his conscious awareness, can now enter his mind because his brain does not have to worry about talking, scheduling meetings, planning his day, or managing his time. […] The important thing is that during rest, the default mode network can open connections between brain regions that are normally too busy trying to keep up with your activity-filled life to talk to each other. This is when true creativity and insight can happen. At this point, Newton’s anterior cingulate cortex, normally hard at work detecting errors and monitoring the outcome of behavior, is now freed to detect weak and strange relationships between numbers, forces, objects, and space. In such a relaxed state, Newton might have only barely noticed the apple falling from the tree. However, his brain would have recorded the event. A seemingly trivial event in the world, an apple falling from a tree, might have triggered a cascade of neural activity which allowed the concepts Newton was contemplating to synthesize into a completely new idea. (Smart 2013: 47-48) Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 As the DMN is a scientifically demonstrated fact, this example depicts the way our brains work in those moments when we are not focused of external environment. Certainly, the apple is an external element (as are the advertisements in the train station or the music from a violin), but all of us understand that Newton begins to think of the falling apple precisely because he was thinking of nothing. At that moment, his mind was just playing. 6. Conclusion: musement as the activity of the brain’s default mode network In this paper, musement and the activity of the brain’s DMN have been presented individually. Nonetheless, at this point, it should be easy to recognize that Newton was playing at musement during the incident of the falling apple; just as Peirce’s, Holmes’s, and Einstein’s DMNs began to light up at those moments of their lives narrated above. Moreover, at this point, it should also be quite straightforward to identify the features of musement presented by Peirce more than a hundred years ago (see Section 1) with the scientific description of the recently discovered DMN. The pure play of the mind [3] begins when the DMN is activated. As the brain’s DMN was discovered in the early years of the 21st century, its activity had no distinctive name previously [1]. That activity begins passively [5], because the DMN works when the demands of external tasks disappear and the mind can wander freely. In this sense, it is an agreeable occupation of the mind with no rules or purpose [1, 2, 3]. When the brain’s DMN is active, participants in experiments report a wide range of mental phenomena, including episodic future thinking, mental simulation, perspective taking, and mind wandering. As noted by Peirce, these imagined events tend to be practical and free of fantasy-like qualities; they are different from reverie [2]. As a defining property of the DMN is its flexibility, its processes may encompass all kinds of reasoning [8] and are open to take different courses [11] (in terms of their content and the goal to which they are applied). The DMN operates using multiple interacting subsystems of the brain: one of them provides information from prior experiences; another facilitates the flexible use of this information during the construction of self- relevant mental simulations. These subsystems converge on important nodes of integration, i.e. the DMN connects the universes of experience [4] adopting the form of an inner dialogue of ideas and images [10]. The DMN is closely connected to creativity. Hence, the activity of the brain’s DMN will be more varied than a method of logic or scientific study [9]. The DMN can help to solve problems [7] because it brings new ideas to the fore: (i) the DMN opens connections between brain regions that are Author’s version. Published in Semiotica 2020; 233: 145–158 https://doi.org/10.1515/sem-2018-0118 normally too busy to talk to each other, (ii) the ability to generate creative ideas is characterized by increased functional connectivity between the inferior prefrontal cortex and the DMN, and (iii) regions of the DMN are more strongly activated during idea generation. Accordingly, the DMN could provide plausible suggestions that need further testing [12] as in the story of Newton and the falling apple. Thus, the activity of the brain’s DMN could be converted into scientific study [6] by developing the new ideas of the DMN. The activity of the brain’s DMN has been identified with the pure play of the mind described by Peirce in The Neglected Argument of the Reality of God. In a general sense, this activity of the mind is related to the capacity of humans to create mental simulations and early decision making. The activation of the brain’s DMN involves connections between different areas of the human brain. Therefore, in this state, we are capable of beginning to connect the different universes of experience. Here, pure play is transformed into musement. Playing at musement, new ideas could arise which bring together what we had never before dreamed of putting together. A hundred years ago Peirce noted the importance of this kind of mental activity and its connection to creativity. Now, the recent discovery of the DMN legitimates Peirce’s ideas about musement in a scientific way. 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