何謂「當下」？

concept of absolute now in Zen Buddhist philosophy Dogen Shobogenzo

In Zen Buddhist philosophy, particularly within the Sōtō school, the concept of the "absolute now" is intrinsically linked to the radical unification of existence and temporality. This perspective is most profoundly articulated by the 13th-century Sōtō Zen founder, Dōgen Zenji (1200–1253), in his philosophical masterwork, the *Shōbōgenzō* ("Treasury of the True Dharma Eye"). The cornerstone of Dōgen’s philosophy of time is found in the *Shōbōgenzō* fascicle titled *Uji*, which translates to "Being-Time" or "Existence-Time". In this text, Dōgen dismantles the conventional, linear understanding of time as an abstract container through which objects and events move from past to present to future. Instead, he asserts that time and being are inseparable; things do not simply exist *in* time, they *are* time. He writes, "The so-called 'sometimes' (uji) means: time (ji) itself already is none other than being(s) (u) are all none other than time (ji)". Within this framework, Zen scholars frequently highlight Dōgen's use of *nikon*, or the "absolute now". For Dōgen, time is radically discrete and discontinuous—a concept termed *zengosaidan* (disconnectedness from before and after). Because the past does not swallow up the present and the future is not a separate destination, the present moment is the ultimate locus of all reality. Accordingly, "All reality—past and future, practice and enlightenment—are to be found in the absolute now of being-time". This metaphysical stance has direct, profound implications for Zen practice. Dōgen posits that the "absolute now" is fully actualized through the spiritual discipline of *zazen* (seated meditation). By sitting in the present moment without grasping at the past or future, the practitioner transcends linear temporality and embodies the entirety of existence. As Dōgen famously declares: "When even just one person, at one time, sits in zazen, he becomes, imperceptively, one with each and all the myriad things, and permeates completely all time". Consequently, in Dōgen's Zen, ultimate truth is not a distant goal to be reached, but the vivid, unfolding reality of existence-time exactly as it is right now.

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• ntu.edu.tw
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• nii.ac.jp
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block universe theory vs presentism in general relativity and quantum mechanics

The debate between the **block universe theory** (eternalism) and **presentism** represents one of the deepest conceptual rifts in modern physics, driven largely by the profound tension between general relativity (GR) and quantum mechanics (QM). In the philosophy of time, "presentism is the theory according to which only the present events are real". Conversely, the block universe theory "posits that all moments in time—past, present, and future—exist simultaneously within a static four-dimensional spacetime continuum". In the realm of **General Relativity**, the block universe is the overwhelmingly dominant interpretation. Due to the *relativity of simultaneity* (RoS)—which proves that spatially separated observers moving at different velocities will disagree on which events happen "now"—an objective, universal present is physically untenable. The classic **Putnam-Rietdijk argument** uses this relativistic structure to mathematically advocate for eternalism. Consequently, maintaining a presentist view in modern cosmology is extremely difficult; philosopher Christian Wüthrich argues that "supporters of presentism can salvage absolute simultaneity only if they reject either empiricism or relativity". However, **Quantum Mechanics** complicates this picture. The probabilistic nature of quantum measurement and wave-function collapse suggests an "open" and undetermined future, naturally siding with presentism or "possibilism" (the *growing block universe*). Physicists like Avshalom Elitzur and Shahar Dolev argue that an objective passage of time is necessary to resolve the GR-QM conflict, noting that "certain quantum mechanical experiments provide evidence of apparently inconsistent histories," implying that spacetime might be subject to objective, dynamic change. Reconciling QM's inherent randomness with the deterministic block of GR remains a fundamental challenge. To bridge this gap, modern researchers propose various unifying frameworks. Some philosophers argue for *adynamical explanations*—focusing on global physical constraints rather than causal, time-evolving dynamics—to resolve problems in foundational physics. Others explore **temporal duality**, a novel cosmological framework attempting to reconcile "the dynamic progression of time in the Standard Model with the eternal, immutable nature of the Block Universe". Ultimately, determining whether time genuinely passes or is merely an illusion experienced by consciousness requires synthesizing the relativistic physics of the macro-universe with the probabilistic physics of the quantum realm.

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• researchgate.net
• nd.edu
• wikipedia.org

neural mechanisms of time perception and the integration of the psychological present

In psychology and cognitive neuroscience, time perception—often termed "chronoception"—is viewed not as a direct sensory input, because humans lack a dedicated sensory organ for time, but rather as a "sophisticated, distributed construction of the brain". The brain integrates subjective temporal flow through widely distributed neural networks, including the prefrontal cortex, basal ganglia, and cerebellum, giving rise to "time consciousness". A foundational concept bridging early psychology and modern neuroscience is the "psychological present," historically referred to as the "specious present." First introduced by E. R. Clay in 1882 and popularized by William James in *The Principles of Psychology* (1890), the specious present defines the temporal window during which a state of consciousness is immediately experienced as "now". Rejecting the notion of an instantaneous, fleeting moment, James famously stated that "the practically cognized present is no knife-edge, but a saddle-back, with a certain breadth of its own on which we sit perched, and from which we look in two directions into time". Modern neuroscience validates and quantifies this early intuition. Researchers such as Marc Wittmann (author of *Felt Time*) and Ernst Pöppel have demonstrated that the brain actively segments perception into temporal units, with the psychological present typically spanning an integration window of roughly three seconds. Through distinct functional levels of temporal processing, the brain fuses successive events into a unitary subjective experience. Furthermore, contemporary findings highlight that this temporal integration is deeply embodied. The neural construction of subjective duration is intimately linked to "interoceptive processes"—the brain's conscious awareness of internal bodily states, such as heartbeat fluctuations. The accumulation of these physiological signals in regions like the posterior insula acts as an internal clock, suggesting that our experience of the psychological present is actively woven from our physical embodiment.

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• arabpsychology.com
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• researchgate.net
• researchgate.net

Ibn al-Arabi concept of the Breath of the Merciful and the continuous creation of the moment

In the Akbarian tradition of Sufism, the universe is not a static, finished product but a dynamic, ever-renewing manifestation of the Divine. At the center of this cosmological vision—formulated by the 12th-century Andalusian mystic Muhyiddin Ibn al-Arabi—are the intertwined concepts of the "Breath of the Merciful" (*Nafas al-Rahman*) and the instantaneous "renewal of creation" (*Tajdid al-khalq*). According to Ibn al-Arabi, whose teachings are crystallized in his masterworks *Fusus al-Hikam* (The Seals of Wisdom) and *Futuhat al-Makkiyya* (The Meccan Revelations), God’s absolute truth (*haqq*) is distinct from His creation (*khalq*), yet the entire cosmos is unified by a process of constant divine renewal. This self-disclosure is conceptualized as an exhalation. Just as human breath is articulated into spoken words, the *Nafas al-Rahman* acts as the primordial matrix of existence—often symbolized as a "dark cloud" (*'ama'*) or mist. Ibn al-Arabi states: "The universe was manifested in the breath of the Merciful which Allah breathed from the Divine Names". Through this compassionate Breath, the hidden potentialities of the Divine Names are spoken into phenomenal existence. Crucially, this exhalation is not a one-time historical event but a ceaseless rhythmic pulse. The Akbarian school asserts that the universe essentially vanishes and is reborn in each successive moment—a process known as *tajdid al-khalq*. Because God is infinite, He never repeats a manifestation; thus, the "words" of Allah are "renewed in continuously new forms every instant". The corporeal world only appears solid and continuous to human senses "because of the close similarity between their ever-new forms". As modern scholars like William Chittick emphasize in their studies of Ibn al-Arabi's cosmology, this continuous creation illustrates a universe in perpetual flux and transmutation. Every atom is sustained by the compassionate exhalation of the Divine, reminding the Sufi seeker that existence is an act of pure grace that requires "spiritual vigilance" to witness the ever-new reality unfolding in the present moment.

• dokumen.pub
• milestonesjournal.net
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• archive.org

Marcus Aurelius Meditations on the infinitesimal nature of the present moment

Within the Stoic tradition, time is viewed not as an expansive landscape to be worried over, but as a sharply narrowed focal point. Stoicism posits that neither the unchangeable past nor the uncertain future truly belongs to us; only the immediate present is within our domain of control. This perspective serves as a profound psychological tool to alleviate anxiety and ground the practitioner in daily virtue. The most authoritative exposition of this idea is found in the *Meditations* of Marcus Aurelius, the Roman philosopher-king. Aurelius frequently reflects on the infinitesimal nature of the present moment, observing that the vast stretches of time before our birth and after our death reduce a human lifespan to a fleeting instant. In Book III, he famously writes, "every man lives only this present time, which is an indivisible point, and that all the rest of his life is either past or it is uncertain". By conceptualizing the present as a microscopic, indivisible point, Aurelius establishes that life is astonishingly brief, yet entirely manageable if tackled moment by moment. Distinctive Stoic concepts anchor this viewpoint. The practice of *prosoche* (continuous vigilance or mindfulness) is essential; it requires focusing one's attention and ruling faculty strictly on the present choice. This discipline is closely tied to *memento mori*, the meditation on mortality, which reminds practitioners that death is always imminent, thereby nullifying the value of posthumous fame or distant anxieties. Because the present is all we possess, it is the only thing we can ever be deprived of. As Aurelius notes, even if one were to live three thousand years, "no man loses any other life than that which now lives, nor lives any other than that which he is now losing". Modern scholars like Pierre Hadot in *The Inner Citadel* highlight that for Aurelius, delimiting the present moment acts as a deliberate "spiritual exercise". It isolates the immediate task, stripping away subjective fears of the future to achieve objective judgment and rational self-discipline. Ultimately, for the Stoic, the infinitesimal present is not a cause for existential despair, but the sole arena where human freedom, moral good, and profound peace can actually be exercised.

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• thestoicgym.com
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• researchgate.net
• dailystoic.com
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• brynmawr.edu

specious present theory in philosophy of mind William James vs E.R. Clay

In the analytic philosophy of mind and empiricist approaches to time consciousness, the "specious present" refers to the brief, extended duration of time that we subjectively experience as "now." This tradition rejects the classical metaphysical view of the present as a mathematically durationless "knife-edge" or instant. Instead, it argues that human temporal perception requires a temporally extended interval to synthesize isolated moments, which allows us to apprehend succession, motion, and change (such as hearing sequential notes as a unified melody). The concept was originally coined by E.R. Clay (also known as E.R. Kelly) in his 1882 book *The Alternative: A Study in Psychology*. Clay distinguished the philosophical, absolute present from our subjective apprehension of it. He noted that what we experience as the present is actually composed of fading sensations, arguing: "The present to which the datum refers is really a part of the past—a recent past—delusively given as being a time that intervenes between the past and the future". This idea was famously adopted and popularized by William James in his 1890 magnum opus, *The Principles of Psychology*. James integrated Clay's insight into his broader theory of the stream of consciousness. James asserted that the "prototype of all conceived times is the specious present, the short duration of which we are immediately and incessantly sensible". James deployed highly distinctive terminology to describe this phenomenon. He conceptualized the specious present as a "duration-block" and famously wrote that the "practically cognized present is no knife-edge, but a saddle-back, with a certain breadth of its own on which we sit perched, and from which we look in two directions into time". To empirically ground the duration of this "saddle-back," James cited contemporary auditory experiments by Wilhelm Wundt and Dietze—who tested subjects' abilities to group rhythmic sounds—suggesting that the nucleus of the specious present spans roughly 6 to 12 seconds. Today, the Clay-James framework remains a foundational touchstone in analytic philosophy for understanding how the brain constructs a unified temporal reality from transient sensory inputs.

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• philosophynow.org
• jhaponline.org
• yorku.ca
• stanford.edu
• encyclopedia.com
• planksip.org

the eternal now and the nature of Brahman as timeless awareness in Advaita Vedanta

In Advaita Vedanta, the ultimate reality, *Brahman*, is defined as pure, timeless, and undivided awareness. The tradition posits that the linear progression of past, present, and future is merely a conceptual construct—a manifestation of *maya* (illusion). Because Brahman is absolute and non-dual, the only genuine temporal state is the "eternal now," an ever-present field of consciousness untouched by the transient phenomena of the material world. Time (*kāla*), space, and causation are viewed as superimpositions on this absolute reality born of human ignorance (*avidya*). Key figures like Adi Shankaracharya established the classical framework for this understanding, declaring, "Brahman satyam, jagan mithya" (Brahman alone is real, the world is an appearance). The *Mandukya Upanishad* is a pivotal text in this discipline, conceptualizing this underlying timeless awareness as *turiya*—the "fourth state" that transcends yet pervades the ordinary states of waking, dreaming, and deep sleep. It describes this state as *"santam shivam advaitam"* (peaceful, auspicious, and non-dual). In the 20th century, sages such as Ramana Maharshi operationalized this wisdom through self-inquiry ("Who am I?"), pointing seekers directly past their temporal ego to the eternal "Witnessing-Self". Distinctive Vedantic terminology further outlines this philosophy. Brahman is fundamentally characterized as *Sat-Chit-Ananda* (Being-Consciousness-Bliss). While chronological time exists on an empirical, practical level (*vyavaharika*), the absolute reality remains completely changeless. By shedding the illusion of linear time, a practitioner can become a *jivanmukta*—one who is liberated while living. A jivanmukta participates in the temporal world but remains anchored in the timeless, acting without doership because they recognize the eternal now. Contemporary commentators increasingly draw parallels between this Vedantic framework and modern quantum physics, noting that both suggest linear time is an emergent illusion rather than a fundamental truth. Ultimately, Advaita Vedanta asserts that "past and future exist only as thoughts happening *now*," inviting seekers to rest in the "eternal stillness that watches the unfolding of life".

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• enlightened-spirituality.org
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maximum rate of information processing and the physical definition of the now in simulation hypothesis

From the perspective of information theory, the universe is fundamentally a computational system, a concept crystallized by John Archibald Wheeler’s "It from bit" maxim. In this discipline, the Simulation Hypothesis and the physical nature of time are scrutinized through the theoretical limits of information processing. A central pillar of this analysis is the Margolus-Levitin theorem, which establishes the absolute maximum rate of information processing allowed by quantum mechanics. Formulated by Norman Margolus and Lev Levitin, the theorem dictates that a physical system can perform at most $2E/\pi\hbar$ elementary logical operations per second, constrained strictly by its average energy. Complementing this is Bremermann’s limit, which bounds computational speed based on mass-energy equivalence. Within this digital physics paradigm, the physical definition of the "now" is fundamentally discrete. Physicist Seth Lloyd, who calculated the computational capacity of the observable universe at roughly $10^{120}$ operations on $10^{90}$ bits, models the universe as a giant quantum computer. In this framework, time does not flow continuously; rather, the "now" is defined by the sequential, discrete updating of quantum information. Each fundamental state-change represents a discrete "tick" of the universal clock, strictly governed by the Margolus-Levitin limit. When applied to Nick Bostrom's Simulation Hypothesis, these theorems impose strict physical limits on any putative base reality. Information theorists argue that even an advanced simulating computer must obey resource finitude, including Landauer’s principle (the thermodynamic cost of computation) and the Margolus-Levitin bound. Because a brute-force simulation of the universe "exceeds current theoretical limits by 19 orders of magnitude," theorists suggest any simulators would be forced to use optimization tricks—such as on-demand rendering tied to the quantum observer effect—to conserve processing power. Ultimately, information theory grounds abstract philosophical arguments in rigorous metrics, viewing reality as "not merely described by mathematics but [as] mathematics being computed".

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• scirp.org
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• nih.gov
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• thearchitect.global
• simulationresearch.org