What This Concept Is About
The causality we understand in everyday life is almost always a single line: first the seed, then the sprout; first the effort, then the reward; first childhood trauma, then adult patterns. The arrow of time shoots from past to future: cause first, effect after. This model is so deeply entrenched that when Buddhist Abhidharma (阿毘達磨) proposes that "two things can be mutually cause and effect at the same time," the first reaction is often: how could that possibly be?
俱有因 (sahabhū-hetu, "co-existent cause") is precisely the category among the six causes (六因, ṣaḍ-hetavaḥ) established in the *Abhidharmakośa-bhāṣya* (《阿毘達磨俱舍論》, composed by Vasubandhu, T1558) that deals with this matter. The six causes in order are: 能作因 (kāraṇa-hetu, "efficient cause"), 俱有因, 同類因 (sabhāga-hetu, "homogeneous cause"), 相應因 (saṃprayukta-hetu, "concurrent cause"), 遍行因 (sarvatraga-hetu, "universal cause"), and 異熟因 (vipāka-hetu, "retributive cause"). The co-existent cause ranks second, and the verse sums it up in five characters:
俱有互为果。
*"Co-existing things are mutually each other's fruit."*
The prose definition is more complete:
若法更互为士用果，彼法更互为俱有因。
*"If dharmas are mutually each other's effective fruit, those dharmas are mutually each other's co-existent cause."*
There are three key terms in this sentence that need to be unpacked one by one.
「更互」(mutual reciprocity) — not a one-way A produces B, but A and B mutually serve as each other's cause and effect. Not a chain, but a ring.
「士用果」(puruṣakāra-phala, "effective fruit") — this is one of the five fruits (五果, pañca-phalāni), referring to the fruit accomplished through the power of exertion (the function of a person, 士夫之用). It differs from the retribution fruit (異熟果, vipāka-phala, the overall retribution of wholesome and unwholesome karma maturing in a future life) and from the flowing fruit (等流果, niṣyanda-phala, the inertia of same-kind continuation). What the effective fruit emphasizes is: this present group of dharmas mutually support and mutually accomplish one another; remove any one of them and the rest cannot stand.
「俱有」(co-existence) — existing simultaneously, operating simultaneously. But note: the treatise repeatedly stresses that "co-existence" is only a necessary condition, not a sufficient one. Two things that happen to appear at the same time do not thereby become mutual co-existent causes.
So the complete meaning of the co-existent cause is: a set of dharmas existing simultaneously, because they constitute one another's functional conditions for operation (mutually being each other's effective fruit), are therefore mutually each other's cause. The criterion is not "simultaneity" but "being mutually each other's fruit."
Three Typical Forms
The treatise gives three types of examples, from coarse to subtle:
1. The four great elements (四大種, catvāri mahābhūtāni) mutually supporting one another. Earth, water, fire, and wind are not four independent substances but four functional dimensions: solidity, moisture, warmth, and motility. In any material phenomenon, the four elements are necessarily all present simultaneously, mutually supporting one another. There is no pure solidity apart from warmth, no pure moisture apart from motility. When one exists, all exist; when one is absent, all are absent. They are not produced in sequence but established simultaneously in mutual dependence.
2. The characteristics (相, lakṣaṇa) and the dharma being characterized. Birth, abiding, change, and extinction are the four common characteristics (本相) of conditioned phenomena (有為法, saṃskṛta-dharma); they arise simultaneously with the conditioned dharma they characterize. When a dharma is "being born," the characteristic of "birth" is simultaneous with the dharma itself — it is not that an independent "birth" comes along first and produces the dharma. But the treatise adds a careful restriction: the dharma can be a co-existent cause for its attendant characteristics, but the attendant characteristics do not necessarily become the co-existent cause of the dharma in return. In other words, the general definition says "mutually each other's fruit," but when applied to specific classes of dharmas, the symmetry is not necessarily perfect; one must judge case by case "according to what is appropriate" (依其所應).
3. The mind and its mind-co-operative dharmas (心隨轉法). This is the most precise layer and the one closest to practice. The mind-king (心王, citta, i.e., consciousness) and the mental factors (心所法, caitta) accompanying it — feeling, conception, volition, and so on — arise simultaneously and operate together. The treatise defines "co-operative with the mind" (心隨轉) by three conditions:
- Time (時): sharing with the mind the same arising, abiding, and ceasing; falling within the same one of the three times — past, present, or future; - Fruit (果): sharing with the mind the same fruit, the same retribution, the same flowing-out; - Wholesome, etc. (善等): being with the mind equally wholesome, unwholesome, or indeterminate (無記, avyākṛta).
Only when all three conditions are satisfied is it called "co-operative with the mind," and only then does it constitute a co-existent cause with the mind. Merely "happening at the same time" is far from enough.
The "Presence-Absence" Criterion and the Parable of Three Staffs
What basis is there for saying that things which are simultaneous stand in a causal relation? The treatise gives an extremely simple criterion: presence-absence (隨有無). If when this dharma exists, that dharma exists; when this dharma does not exist, that dharma does not exist — then one can say a causal relation holds between them. The co-existent dharmas are exactly like this: when one exists, the rest all exist; when one does not exist, the rest all do not exist.
How to imagine "simultaneous mutual causality"? The treatise uses an ingenious simile: three staffs leaning on one another (三杖相依). Three wooden staffs incline at the same time, their tops leaning against each other, each supporting the others to stand. No single one stands up "first" and then supports the other two — they are simultaneously each other's supporting condition. Pull out any one, and the other two immediately fall.
But the treatise immediately adds: for the three staffs to stand, there must also be maintaining conditions such as rope binding, hooking, and level ground. Likewise, among dharmas, besides the co-existent cause, there may also be involved at the same time the homogeneous cause (the inertia of sequential continuation), the efficient cause (the passive condition of non-obstruction), and so on. The co-existent cause does not operate in isolation; it is embedded in a more complex network of causes and conditions.
Its Relation to the Concurrent Cause
The treatise states clearly: the substance of the concurrent cause is precisely the co-existent cause. The dharmas they cover overlap, but the angle from which they are named differs. The co-existent cause emphasizes "being mutually each other's fruit" — like traveling merchants leaning on each other as they pass together through a dangerous road; the point is that each is the condition for the other completing the whole journey. The concurrent cause emphasizes "equal correspondence" — the mind and mental factors being fully synchronized in their object (所緣, ālambana, the same object), their cognitive mode (行相, ākāra, the same way of cognizing), their time (the same moment), and their basis (所依, the same sense faculty); like traveling merchants sharing provisions and working together, the point is coordinated pace and resonance at the same frequency.
To use a rough but intuition-friendly analogy: the co-existent cause is like a reciprocal relationship in structural mechanics (you support me, I support you); the concurrent cause is like the synchronization of voice parts in a choir (the same beat, the same key, the same piece).
"Co-existence" ≠ "Co-existent Cause"
This is the point the treatise labors hardest to distinguish. Some dharmas, though co-born and co-present, do not constitute a co-existent cause:
- Between the secondary characteristics (隨相: the birth-of-birth, abiding-of-abiding, change-of-change, extinction-of-extinction) and the primary dharma; - Between the secondary characteristics of a mind-co-operative dharma and the mind itself; - Among some co-born material forms (造色); - Between acquisition (得, prāpti) and what is acquired — these two are not even necessarily simultaneous; they may arise at different times.
Those that do not share the same retribution fruit, the same flowing-out, and other such conditions cannot be judged as co-existent causes merely by "happening to be simultaneous." This restriction is extremely important: it pulls the co-existent cause back from an ontological description ("they are there at the same time") to a functional criterion ("they are each other's operating conditions").
Walking Through It in Daily Life
Let us walk through every element of the co-existent cause using a scene all too familiar to contemporary people.
Scenario: Scrolling Your Phone at Midnight
At one in the morning, you lie in bed scrolling short videos. In this seemingly simple act, at least one set of "co-existence" relations is in operation.
Layer one: the mutual dependence of the four great elements. The hand holding your phone — the solidity of bone (earth), the moisture of blood (water), the warmth of body temperature (fire), the motility of breath and fine muscle movement (wind) — is not four things assembled together, but four dimensions established simultaneously in mutual dependence. Without body temperature, blood would not flow; without blood flow, muscles could not sustain tension; without muscle tension, the posture of the skeleton could not be maintained. Remove any one dimension, and the other three immediately collapse. This is what the three-staffs-leaning means at the level of the body.
Layer two: the mind and its mind-co-operative dharmas. At this moment your consciousness (eye-consciousness or mind-consciousness) is apprehending the images on the screen. Arising simultaneously with this consciousness are feeling (受, vedanā, subtly pleasant or unpleasant), conception (想, saṃjñā, grasping and recognizing: this is a funny video, that is a news item), volition (思, cetanā, the impulse of will: keep scrolling or put the phone down), and contact (觸, sparśa, that "touch" of the union of sense faculty, object, and consciousness). They do not appear in a queue — it is not that consciousness comes first, then feeling arrives, then conception arrives. They arise in the same moment, abide in the same moment, cease in the same moment; they belong to the same retribution (all being the karmic fruit-body of this lifetime); they are equally indeterminate or covered (at this moment not necessarily wholesome or unwholesome, but a kind of turbid habitual state). Satisfying the three conditions of time, fruit, and moral quality, they are mind-co-operative dharmas and constitute a co-existent cause with the mind.
The place where it is easiest to map wrong: Many people understand feeling as "my emotional reaction," conception as "my thoughts," and volitional formation (行, saṃskāra, i.e., volition) as "my actions." No. Feeling is the bare reception of pleasant/painful/neutral at that moment — extremely subtle, far before you paste the label "I'm anxious" onto it. Conception is grasping at characteristics — recognizing a patch of light and color as "this is a character," "that is a face" — it is recognition, not thinking. Volition is the direction of will — approaching or avoiding — not an external bodily action. Confuse these three and the whole walkthrough falls apart.
Layer three: contact and feeling as mutual cause and effect. The Vibhāṣā masters in the treatise specifically discuss this: contact (the union of sense faculty, object, and consciousness) and feeling (reception) arise simultaneously, are mutual co-existent causes, and are mutually each other's fruit. In your phone-scrolling scenario: precisely because there is contact (that touch of the union of eye, screen light, and eye-consciousness), there is feeling (that fleeting subtle pleasantness); but conversely, precisely because there is feeling (that bit of subtle pleasantness), contact is "activated" as a meaningful experiential event rather than remaining merely the physical event of photons striking the retina. They are not in a sequential relation but a simultaneous mutual-achievement relation.
Layer four: the presence-absence test. Now do a thought experiment: if feeling were removed at this moment — you look at the screen but there is not a trace of pleasant, painful, or neutral — would you keep scrolling? No. Your finger would stop, because the subtle approaching force (volition) driving "one more video" has lost its fuel. Conversely, if contact did not obtain — say your eyes are closed and the screen is off — feeling could not arise either. When one exists, all exist; when one is absent, all are absent. The presence-absence criterion can be intuitively grasped here.
Layer five: what is not a co-existent cause. While you scroll, a car passes outside the window. The engine sound of that car and your eye-consciousness do indeed "exist simultaneously," but they do not share the same retribution or the same flowing-out, and they do not constitute your mind-co-operative dharmas; therefore they are not a co-existent cause. At most they are an efficient cause (not obstructing your continued scrolling), but they are certainly not in a relation of "being mutually each other's effective fruit." This is the everyday version of "co-existence" ≠ "co-existent cause": being present at the same time does not equal being mutual conditions.
Scenario Extension: "Three Staffs" in an Intimate Relationship
Two people living together long-term gradually form a reciprocal structure from each other's personality, habits, and emotional regulation styles. A's anxiety needs B's reassurance to "stand"; B's sense of self-worth needs A's dependence to "stand." Remove either party, and the other's pattern immediately collapses. This is not linear causality of who influenced whom first, but a co-existent structure of simultaneous mutual achievement.
But note the restrictions in the treatise: not everything "simultaneously present in the same relationship" is a co-existent cause. A's anxiety and the engine sound of the car outside are still not a co-existent cause. Even between A's anxiety and the dinner B is making at this moment, though they "co-exist," they are not necessarily mutual effective fruits. Only when the conditions of presence-absence and shared fruit are satisfied can one say they constitute each other's co-existent cause.
Why Contemporary People Need It
1. Breaking the Obsession with Linear Causality
Contemporary people are especially good at finding "causes": family of origin, childhood trauma, genes, hormones, algorithmic recommendations. These are of course real causal conditions, but most of them fall into the category of the retributive cause (past karma maturing) or the homogeneous cause (the continuation of inertia). What the co-existent cause reveals is another dimension: What is the reciprocal structure that is maintaining this state right now?
When a person says "I am anxious because my childhood was insecure," that is backward-looking linear causality. The co-existent-cause perspective asks: right now, which of your physical and mental states are mutually supporting and mutually feeding your anxiety? Your breathing pattern (wind element), muscle tension (earth element), subtle unpleasant feeling (feeling), the recognition "this is a threat" (conception), the volitional impulse "I must do something" (volition) — these are not "results" of anxiety; they are the co-existent causes by which anxiety exists at this very moment. Pull out any one of these staffs, and the present structure of anxiety begins to loosen.
This is not denying past causes, but adding a neglected dimension: the past cause is already past, but the reciprocal structure of this moment is what keeps that fruit "standing."
2. Understanding the Causal Power of "Simultaneity"
There is an intuition in the algorithmic age: the recommendation system "first" analyzes your preferences, "then" pushes content to you, "therefore" you have become what you are now. This is a linear narrative. But the real structure is closer to the co-existent cause: your clicking behavior and the algorithm's recommendations are simultaneously mutually constituting — each of your pauses instantly reshapes the recommendations, and the recommendations instantly reshape your attention allocation. Neither side is "first." They are mutually each other's effective fruit: without your dwell-time data, this version of the algorithm's ranking would not hold; without this version of the ranking, this particular pause of yours would not occur.
Understanding this is not to blame the algorithm, but to see: you are not a passive receiver unilaterally shaped by an external force. You are one staff in this reciprocal structure. If your staff is pulled out (for example, by putting down the phone and cutting that feedback loop), the other one cannot stand either.
(The analogy must stop here: algorithmic recommendation and the co-existent cause share only a structural similarity, not an equivalence in doctrine. The co-existent cause discusses the mutual dependence of conditioned dharmas at the level of the moment, with strict conditions such as "same retribution, same flowing-out"; algorithmic systems do not satisfy these conditions. This analogy aids intuition but cannot replace precise understanding of the dharma's meaning.)
3. Direct Use in Practice
When contemplating the five aggregates (五蘊, pañcaskandha, the five aggregates), if one only sees the linear twelvefold dependent origination of "feeling → craving → clinging → becoming," it is easy to think: as long as I insert mindfulness between feeling and craving, I can cut the chain. This is of course an effective antidote, but the co-existent-cause perspective adds a subtler layer: feeling and contact are mutually causal simultaneously. You cannot "first have contact, then intercept before feeling" — they are a reciprocal structure in the same moment. This means contemplation cannot merely be "stepping on the brake between two links," but must simultaneously see the entire reciprocal structure, see how the three staffs lean on one another and stand.
In the *Saṃyuktāgama* (《雜阿含經》), the Buddha said: "此有故彼有，此生故彼生；此无故彼无，此灭故彼灭" — *"When this exists, that comes to be; with the arising of this, that arises. When this does not exist, that does not come to be; with the cessation of this, that ceases."* These four lines are often read as linear dependent origination, but "when this exists, that exists" can equally describe the presence-absence relation of the co-existent cause: when this is present, that is present; when this is absent, that is absent — without any temporal priority.
4. Loosening Attachment to "Self"
The deepest use is here. We intuitively feel that "I" is an independent, self-existing subject, and then "I" experiences the world, "I" creates karma, "I" receives its fruits. The analysis of the co-existent cause dismantles this intuition: the so-called "I" is nothing more than a set of simultaneously interdependent dharmas — the four great elements mutually supporting, mind and mental factors mutually constituting, characteristics and what is characterized arising together. No single staff is the "subject" with the rest as "appendages." The three staffs lean on one another equally; remove any one, and the structure called "I" does not hold.
This is not a philosophical proposition to be "believed," but a structural description that can be verified in present-moment contemplation. The treatise gives the criterion: presence-absence. Try to find, in meditative contemplation, a consciousness that exists independently without depending on feeling, or a feeling that exists independently without depending on contact — you will not find one. When one exists, all exist; when one is absent, all are absent. The sense of "I" as an independent, self-existing subject begins to loosen under this observation.
Common Misreadings and Clarifications
Misreading 1: "The Co-Existent Cause Is Just Simultaneous Occurrence"
This is the most common narrowing. The treatise spends a great deal of space distinguishing: simultaneous existence (co-presence, co-birth) is only a possible condition, not a sufficient one. Acquisition and what is acquired may be simultaneous or may be at different times; some co-born material forms do not mutually serve as effective fruits; secondary characteristics and the mind, though arising together, do not satisfy the condition of the same retribution. The criterion is always "being mutually each other's effective fruit," not "happening to be simultaneous."
Equating the co-existent cause with "simultaneity" is like equating "causation" with "temporal contiguity" — Hume long ago pointed out this fallacy, and the *Abhidharmakośa* had already drawn this line with complete clarity in the fourth century CE.
Misreading 2: "Mutual Causality Is Circular Reasoning"
Some people, on hearing "simultaneous mutual causality," immediately think it is logical circular reasoning (A because of B, B because of A, so nothing is explained). But the co-existent cause is not about an epistemological argumentative structure; it is about an ontological structure of interdependence. The three staffs leaning on one another is not a "circular proof" but "structural reciprocity" — just as the stones of an arch bridge do not "circularly explain why the bridge does not fall," but "are each other's condition for the bridge not falling." The treatise uses "presence-absence" to determine this: this is not logical deduction but factual observation — pull out one staff, do the rest collapse? If yes, then the causal relation holds.
Misreading 3: "The Co-Existent Cause and the Concurrent Cause Are the Same Thing"
The treatise states clearly that "the substance of the concurrent cause is precisely the co-existent cause," but the angle of naming differs. The co-existent cause broadly covers all interdependent relations among conditioned dharmas (between the four great elements, between characteristics and what is characterized, between mind and mental factors) — its scope is extremely wide. The concurrent cause is limited strictly to the relation between mind and mental factors, and additionally requires equal correspondence in the four aspects of object, cognitive mode, time, and basis. One could say: the concurrent cause is a specialized subset of the co-existent cause in the domain of mental dharmas, with the extra constraint of "same frequency, same rhythm" added.
The traveling-merchants simile is precise: the co-existent cause is "leaning on each other to walk the dangerous road together" (each is the condition for the other completing the journey); the concurrent cause is "sharing provisions and working together" (coordinated pace, eating together, dwelling together, traveling together). The former emphasizes structural interdependence; the latter emphasizes synchronized resonance.
Misreading 4: "Since They Are Mutually Causal, There Is No Need to Distinguish Primary from Secondary"
The treatise states explicitly in the section on "characteristics and the dharma being characterized": the dharma can be a co-existent cause for its attendant characteristics, but the attendant characteristics do not necessarily become the co-existent cause of the dharma in return. Although the general definition speaks of "mutual reciprocity," when applied concretely the symmetry is not necessarily perfect. The four characters 依其所應 ("according to what is appropriate") are a qualifier that recurs throughout the treatise, meaning: one must judge according to the actual relation of the specific class of dharmas; one cannot mechanically understand "mutual causality" as "perfect symmetry."
The implication for contemplative practice is: although mind and feeling are mutual co-existent causes, when applying an antidote, starting from "feeling" and starting from "contact" may not have the same effect. The structure is interdependent, but the point of entry for practice differs in its degree of convenience.
Misreading 5: "This Is Ancient Physics, Unrelated to Liberation"
The mutual dependence of the four great elements and the three-staffs-leaning sound like a discussion of material structure. But the treatise classifies the co-existent cause within the six causes — the six causes exist to explain how all conditioned dharmas arise, how they continue, and how they cease. Its ultimate purpose is not physical curiosity but this question: How is suffering (苦, duḥkha) maintained in the present moment? And how can it be loosened in the present moment?
If suffering were merely a linear chain extending from the past to the future, the only antidotes would be "tracing back to the source" or "waiting for the karmic fruit to exhaust itself." But the co-existent cause tells you: suffering is right now being supported by a set of simultaneously interdependent conditions. Any one of those staffs is an entry point available in the present. You do not have to wait until childhood trauma is "completely healed" to be released from anxiety — this moment's breathing, this moment's way of grasping characteristics, this moment's direction of volitional formation: all are staffs in that reciprocal structure, and all can be points of entry for contemplation and adjustment.
This is the true place of the co-existent cause on the path of liberation: it liberates causality from the "past → future" timeline and lets you see the interdependent structure of "this moment" — and "this moment" is precisely the only place where one can act.
*A final note.* The analysis of the co-existent cause is extremely precise; the treatise sets limit upon limit and distinguishes step by step, reading like a paper on structural mechanics. This precision is itself an antidote: it counteracts our vague intuition of "good enough" and "roughly simultaneous probably counts as causality." What contemplation on the path of liberation needs is precisely this kind of "according to what is appropriate" precision — not smashing everything into a hazy feeling of "all things interconnected," but seeing clearly: right now, which staffs are supporting one another? Pull out which one does the structure of this suffering begin to loosen?
The three staffs lean on one another: rope binding, hooking, level ground. When the conditions are complete, they stand; when the conditions disperse, they fall. No "prime mover" is needed, and no "final judgment" needs to be awaited. The structure of this moment is the causality of this moment.