Past mind is one of three positions citta (心, the moment-of-knowing event) can occupy in Buddhist temporal analysis: past (過去 / atīta), present (現在 / paccuppanna), and future (未來 / anāgata). What makes it interesting — and counterintuitive — is that the term is grammatically in the nominative ("past mind") but ontologically it has already vanished. It exists as a *classification* of what is no longer there. To hold this concept carefully is to begin to see how the early teachings dismantle the "I" that supposedly remembers, owns, and continues across time.
一、這個概念在說什麼
1. 把定義的三個零件拆開
古典條目給的是：「已於過去剎那生滅的心識。」讓我們把每一塊按經典定義拆準。
心識 (citta-vijñāna) — here essentially 心 (citta) with 識 (vijñāna) as gloss. In the Abhidhamma framework that this term most naturally belongs to, *citta* is the principal moment of knowing — a singular event of cognizance that arises, sustains for an instant, and passes. It is not a "mind-stuff" that persists, not a small homunculus inside the head, not a thing that "has" thoughts. It is the act of cognizing itself. (In Yogācāra the 識 layer is more elaborately split into eight, but for the present concept the relevant point is the same: a knowing-event that has duration of a moment.)
Importantly, *citta* is technically distinct from 心所 (cetasika, mental factors that accompany it — vedanā feeling, saññā perception, cetanā volition, etc.). When a classical text says 過去心, it refers to the citta event; the factors were there alongside it but they are not the referent. For our purposes, 心 = the principal knowing-moment.
剎那 (kṣaṇa) — an instant. Different traditional reckonings give different lengths (the Abhidhammattha-saṅgaha mentions 7,560 ksanas per blink of the eye; other sources give different calibrations). What is consistent across schools is the *function* of kṣaṇa: a unit so small that nothing of lasting substance can be located within it. It's the "atom" of experience, used precisely to deny continuity on the inside.
已於過去剎那生滅 — "already arisen and ceased in a past kṣaṇa." This is the operational definition. 生 (arising) and 滅 (cessation) are not optional add-ons; they are *constitutive* of citta. To be citta is to arise-pass. Therefore to be 過去心 is to have completed this arising-passing. The qualifier 已 (already) marks that the process is finished; nothing further is happening to that mind-event.
So: 過去心 = a citta event that has already gone through its full lifecycle of arising and passing in some prior instant. It is named "past" precisely because it is *no longer occurring*. The grammar of the term encodes its own absence.
2. 它在哪裡 — 這個概念在整個解脫道裡的位置
Past mind sits inside two larger maps, and seeing both is essential.
(a) The Abhidhamma "three-times" classification of citta. Among the many ways citta is classified in the Abhidhamma (by door — eye, ear, mind; by object; by nature — wholesome, unwholesome, resultant, functional; by plane — sense-sphere, fine-material, immaterial; etc.), one of the cleanest is by time (kāla). Citta at any given moment can be characterized as past, present, or future relative to that moment's vantage point. This is not a metaphysical claim about time; it is an analytical tool — the question "is this citta past, present, or future?" is asked *from within* the temporal flow, not from an external observer's view. Past citta are those that have already completed; future citta are those that have not yet arisen (in the technical sense — citta is conditioned by prior causes, and the next citta's arising is already implicit in the present configuration). Present citta is the one moment currently arising.
This classification matters for practice because it clarifies what can be an object (ārammaṇa) of present knowing, and what cannot. Present citta can take as object a past event (memory), a present object (direct sense encounter), or a future object (anticipation, imagination). But *past citta itself* — the original knowing-event — is not directly observable. By the time you try to look at it, it is past again; the looking is a new citta. This is one of the foundational moves in Buddhist epistemology.
(b) The Prajñāpāramitā "三心不可得" (three-time-mind cannot be obtained). The classical place where this concept becomes a *gateway* to seeing through self is the *Vajracchedikā Prajñāpāramitā* (《金剛經》, the Diamond Sutra), Kumārajīva's translation:
「須菩提！過去心不可得，現在心不可得，未來心不可得。」
(*"Subhūti — past mind cannot be obtained; present mind cannot be obtained; future mind cannot be obtained."*)
This line sits within the larger argument of the sutra that "the so-called mind / Buddha / bodhisattva / Dharma are all named with provisional words, and are not to be grasped as such." When the Buddha asks Subhūti to inspect each of the three times for the mind, the teaching is that no mind — not the past one, not the present one, not the future one — can be located as a fixed, ownable, graspable thing. What you find when you look for "the past mind that was mine" is not an object; it is the re-arising of looking itself.
This is not a denial that there was past knowing. It is a denial that any of it *hangs together* as a self-essence available to be retrieved, owned, identified with. The Diamond Sutra is doing the same work as the *Pañcaviṃśatisāhasrikā Prajñāpāramitā* and other Prajñāpāramitā texts when they say that *citta* itself is "no-citta" — not because it doesn't function, but because no controller, no substance, no owner can be found inside it.
**(c) The relationship between 過去心 and what *does* persist.** Beginners often ask: if past citta is gone, how do habits persist? How does kamma ripen? How do memories work? Three classical answers:
- 習氣 (vāsanā) — tendency / imprint. The *Sutta Piṭaka* (e.g., AN 7.79 on the "taints" that beset the mind) and Mahāyāna texts (the Yogācāra's analysis of *vāsanā*, the *Surangama*'s "see-saw of vexation and enlightenment") both speak of residual tendencies that carry forward. These are not the past citta themselves; they are the *karmic imprints* those citta moments left behind. Functionally important, but ontologically distinct. - 果報 (vipāka) — the ripening result. In the Abhidhamma, a past wholesome or unwholesome cetanā (volition) produces a present *vipāka* — a result-citta — in the appropriate conditions. The result is *new* citta; it is not the original citta redux. - Memory itself (smṛti / sati). When you recall yesterday's event, what is occurring is a present citta whose *object* is a past event. The memory is *present* mind; the *object* is past. This distinction is decisive.
If we fail to keep these three separate, "past mind" becomes a metaphysical landfill where everything we don't understand gets dumped. The classical analysis is much sharper: past mind = gone. What remains = its conditioning effect on the next citta.
3. The classical "image" question
A note on what might be expected here: the five aggregates have their famous images (色如聚沫, 受如水泡, 想如野馬, 行如芭蕉, 識如幻 — form like foam, feeling like a water-bubble, perception like a mirage, formations like a banana tree, consciousness like an illusion). The three-time-mind does not have a parallel set of "one-image-per-time" in the canonical corpus I'm aware of. What it has instead is a *frame*: the negative of 不可得 (cannot be obtained). The teaching moves by subtraction — "look for the past mind; you won't find it" — rather than by positive imagery. I want to flag this rather than invent images, because the integrity of the concept depends on its *aporetic* character: it is precisely what cannot be pinned down as a thing.
二、生活裡的走查
Let us walk through a concrete situation. Pick something almost everyone has done: replaying a difficult conversation from yesterday.
You said something you regret at a meeting. Today, on your commute, you replay it. Let's walk this strictly through the classical scheme.
Step 1 — Inventory what actually happened yesterday. During that meeting, a stream of citta moments arose and passed. If we count them in classical terms, each *eye-contact*, each *heard phrase*, each *internal "they're going to push back"* was a citta event with its own arising and ceasing. By the time the meeting ended, those thousands of citta events were complete. They are now what the term 過去心 names. They are no longer occurring. There is no present moment at which "the citta of saying that thing" can be re-entered.
**Step 2 — What is happening *now*, on the commute?** Today, as you replay, what is occurring is a *new* stream of citta. These are 現在心 (present mind), taking a *past event* as their object. The replay-citta has a past object (the meeting) but is itself fully present in its arising and passing. Crucially: the replaying is not the past. The replaying is happening now. Many people slide between these and end up saying "the past keeps happening to me" — but what keeps happening is *new* citta moments that keep *referring* to a past.
Step 3 — What persists from the past? Yesterday's citta is gone, but it left imprints: a tendency toward self-criticism (习气), perhaps an unwholesome *vipāka* showing as the bodily feeling of shame in the chest, and a memory trace that allows the *ālambana* (object) to be re-presented today. None of these is the past citta. All of them are present phenomena *conditioned by* past citta.
Step 4 — Where people map the concept wrong. Here is the most common mis-mapping in real life:
"I am replaying *my* past mind."
The hidden assumption is that there is a *me* who owns the past mind and who is now retrieving it. In classical terms, the *retrieval* is new citta; there is no "me" that has been there continuously across yesterday and today. The continuity is constructed by *nāma-rūpa* — the appearance of naming-and-form across moments — and then appropriated by *māna* (conceit: "I am"). So the very sentence "I am replaying my past mind" already contains two unexamined assumptions: that there is a continuous "I," and that the past mind is a retrievable object. Both unravel under the three-time-mind analysis.
**Step 5 — Where it *can* be mapped correctly.** What *can* be said in the classical frame:
- "A past stream of citta happened, conditioned by prior causes." ✓ - "Imprints of those citta are influencing this moment's cognition." ✓ - "The current replaying is *now*-arising citta taking a past object." ✓ - "When I look for *the* past mind as a thing I can get hold of, I cannot find it." ✓ (this is the Diamond Sutra move) - What *cannot* be said: "The past mind is still there somewhere." "I am identical with the one who said it." "The past citta is exerting direct causal power *as itself*." These are reifications.
A second scenario — the recurring photo-album feeling.
You scroll through photos from three years ago. A strange ache. Classical walkthrough: the citta of being photographed, of that summer, of that relationship — all 過去心, gone. The present ache is a new citta whose object is a *constructed representation* of that time (photos, dates, sequences your mind stitches). What the photos actually capture is light that hit a sensor once. The "younger self" you see is no more that self than a shadow is the body — appearances that look like persistence but are configurations re-presented. The ache is not from the past returning; it is from a present construction that is taking *past* as its object.
A third — the trauma-recall scenario, briefly.
When a traumatic event intrudes on present consciousness, contemporary trauma therapy often speaks of the past "not being over." A classical Buddhist analysis does not deny the intensity. It says: (1) the original citta moments of the event are past — they cannot be retrieved or re-experienced as such; (2) the *vāsanā* of those moments is intense and is being re-activated by present conditions; (3) the present *experience* of intrusion is now-arising citta with a past object. Working with this, classical practice (e.g., in *Satipaṭṭhāna* and in the contemplative Mahāyāna traditions) does *not* try to "find" the past citta and fix it. It works with the present citta stream — its vedanā, its tendency to seize — *now*. The past is gone; the present is where liberation has to operate.
Where mapping goes wrong, summarized. The single most frequent mis-mapping I encounter in conversation is this: people hear "past mind" and substitute *memory* (which is present mind about past object). With that substitution, the whole liberating edge of the concept disappears — because memory feels retrievable, ownable, narratable. The classical concept insists: not even memory is *the* past mind. Memory is the present's encounter with the past, on its own terms.
三、當代人為什麼需要它
A concept that insists "the past is gone — but not as you think" sounds esoteric until you notice how much modern suffering is organized around a confusion about exactly this point. Four places where the teaching speaks directly to contemporary life.
1. Rumination, anxiety, and the false continuity of "me"
Modern clinical literature on rumination (the repetitive past-focused negative thinking implicated in depression and generalized anxiety) describes the experience as "getting stuck in the past." The metaphor is wrong in exactly the way Buddhism diagnoses: it implies a stuck *entity*. In classical terms, rumination is a continuous *stream* of new citta moments, each taking the previous one as object, each carrying *vedanā* (feeling tone) of dukkha, each *conditioned* by past unwholesome cetanā but *not identical* with it. The intervention this analysis suggests is not "stop remembering" (impossible, because you cannot stop new citta from arising on its own). The intervention is closer to what *Satipaṭṭhāna* does: *notice the stream as a stream*, see that each citta that arises also passes, and *do not identify* with the "I-am-the-one-who-keeps-thinking-it" that the stream itself constructs.
A useful contemporary analogy — with the caveat that this is an analogy, not a proof: contemporary neuroscience has begun to question the "memory as storage" model. *Engram* research shows that what we call "remembering" is an active reconstruction, not a retrieval; each act of remembering literally alters the trace. Buddhism's analysis is more radical — it never accepted the storage model in the first place. Past citta is not stored; it is gone. What gets reactivated is a *configuration* in present citta's conditions. (Caveat: neuroscience does not yet have a settled model here; the analogy is suggestive, not probative.)
2. Identity as "my past"
Contemporary culture — therapeutic, social-media, political — is saturated with the demand to *own* one's past: tell your story, claim your trauma, narrate your origin. There is real therapeutic value in some of this, and Buddhism is not in the business of denying people's lived experience. But the three-time-mind analysis adds a layer: the past you are being asked to own is a construction happening in present citta, not a fixed object available for retrieval. The "I" who owns the past story is itself a *present* citta construction, projecting itself backward. If you *hold* the past lightly — neither denying what happened nor reifying "my past self" — the same material can be present without becoming a cage. The Diamond Sutra's "past mind cannot be obtained" is not nihilism about the past; it is freedom from being *captured* by the past.
This connects to a deep feature of the *Middle Way*. Buddhism is not interested in whether the past "really happened" in some external sense; it is interested in how *present* citta relates to past objects. The past is real *as an object of present cognition*; it is not real *as a self-essence one can own*. Modern readers who slide into either pole — denying the past's effects (a kind of spiritual bypassing), or reifying the past as a defining identity (a kind of biographical determinism) — miss the middle.
3. Karma and the impossibility of "undoing" the past
Modern life offers countless "reset" fantasies: delete the email, cancel the post, restart the relationship, take the new job. The classical teaching on past citta points to a sobering recognition: past citta cannot be revoked. Its imprints are real; its ripening in vipāka happens under appropriate conditions. There is no "delete" button on kamma. But — and this is equally classical — kamma is *conditioned ripening*, not mechanical predestination. What can change is the present citta stream's relationship to the past object, and the new cetanā one is generating now. The past is fixed; the *future* is open in the sense that present volition shapes what comes next. The three-time-mind analysis, when applied to the whole of past-present-future, is the structure within which ethical action makes sense.
4. "Letting go" as something more precise than a mood
The contemporary self-help culture offers "letting go of the past" as a feeling-state to be cultivated. Buddhism's analysis offers something stricter: you cannot *let go of* a past citta, because the past citta is gone. What you can do is stop *re-arising* unwholesome citta in relation to it. "Letting go" is therefore not an act performed on a thing; it is a *cessation of fabrication (saṃskāra)* in the present. This is harder to *feel* and far more liberating than the mood-version. It points toward the *nirodha* (cessation) aspect of the Four Noble Truths — not as escapism, but as the recognition that which has arisen will, on its own, cease, and that the clinging to it can also cease.
四、常見誤讀與澄清
I want to lay these out sharply because each one erases a different facet of the concept.
1. 過去心 = 記憶 (memory)
This is the most common conflation. It is wrong. Memory (smṛti / sati in its ordinary sense) is a *present* citta that has a past object. The meeting you recall is not "your past mind." The recalling is happening now. The meeting itself, as it was experienced, is what classical analysis calls 過去心 — gone, completed, no longer accessible except as an object of *present* cognition.
This matters because if past mind *were* memory, then the whole teaching becomes "you can't quite remember clearly," which is trivial. The actual teaching is much sharper: *that mind* (the moment of original cognizing) does not exist anywhere now. What exists now is *new mind* taking *that* as object.
2. 過去心 = 潛意識 / 阿賴耶識 (subconscious / storehouse-consciousness)
Some modern readers, hearing that past citta leaves imprints and produces results, leap to a "subconscious mind" or ālaya-vijñāna model in which the past is *stored*. This is contested even within Buddhism. The Abhidhamma — which is where 過去心 is most technically at home — does not posit a storehouse. It analyzes persistence through (a) the *continuity of conditions* (the next citta is conditioned by the previous), (b) the *vāsanā* or tendency-quality of cetanā, and (c) the *vipāka* mechanism through which past cetanā produces present result. Yogācāra does develop ālaya-vijñāna as a deeper stratum that holds *bīja* (seeds), but this is a sophisticated doctrinal elaboration, not a common-sense given. For the term 過去心 in its classical usage, assume no storage, and read the persistence of karmic results as the conditioning of new moments by old — not as a hidden warehouse.
3. 過去心不可得 = 過去不存在
A serious philosophical misreading. The Diamond Sutra's "cannot be obtained" does not mean "the past is not real." It means the past *mind* — as a self-essence, as a thing one can grasp, as an "it" — is not obtainable when you look. Past events condition present experience; past kamma ripens; past actions have consequences. What is denied is the reification of the past into an ownable, nameable, retrievable object. This is the same move that Buddhism makes about *Dharma*, *Buddha*, *self*: not denial, but refusal to reify. "Cannot be obtained" is a verb-claim about grasping, not an existence-claim about what is being pointed at.
4. 過去心 = the "real me" who used to be
Many people use the term "past self" as if there were a continuous identity that *was* in the past. The classical analysis denies this. There was a *stream* of citta moments, none of which was a "self." What is now constructed as "my past self" is a *present* citta event that has a constructed representation as its object. The continuity-feeling is itself a fabrication (saṃskāra). This is not nihilistic — the stream is real, the conditioning is real, the karmic continuity is real — but the *self that runs through it* is a retrospective projection. The Buddha's analysis of *nāma-rūpa* and *vijñāna* in dependent origination is the technical support for this: what appears as continuity is a sequence of causally related but discontinuous moments.
5. Letting go of past mind = forgetting / suppression
Some readers hear "past mind cannot be obtained" and conclude the practice is to *stop remembering*. This is wrong on two counts. First, classical Buddhism does not ask for memory-suppression; sati (mindful remembering) is one of the five faculties. Second, the point is not to make the past *absent* but to change the present citta stream's *relation* to past objects — from grasping (*upādāna*) to clear knowing. The past is allowed to be known, but not possessed, not narrated as identity, not held in a way that generates dukkha. This is a different operation than suppression. It is closer to what *Satipaṭṭhāna* calls seeing the past as past, the present as present, without collapsing the categories.
In sum: 過去心 is a deceptively simple term. It names a class of events that, by definition, no longer exist. Holding it well means holding several distinctions at once — past citta vs. memory, past citta vs. imprint, past citta vs. ripening result, "cannot be obtained" vs. "did not happen." When these distinctions are kept, the term stops being an obscure Abhidhamma category and becomes a quiet instrument for loosening the grip the past has on the present — not by denying the past, but by refusing to mistake the present's *image* of the past for the past itself.