作用道理

I. What This Concept Is About

1. The Second of the Four Modes of Reasoning

The *Yogācārabhūmi-śāstra* (瑜伽師地論) teaches yogic practitioners to observe all phenomena with four modes of reasoning (yukti):

- 觀待道理 (apekṣā-yukti, the mode of dependence) — phenomena are established in dependence on other factors - 作用道理 (kāryakāraṇa-yukti, the mode of function) — phenomena each have their own activity, and causes and conditions each have their efficacy in bringing about results (the subject of this essay) - 證成道理 (sādhana-yukti, the mode of validation) — by means of scriptural authority, direct perception, and inference, the meaning to be established is set in place and proven - 法爾道理 (dharmatā-yukti, the mode of thusness) — the intrinsic nature of phenomena as they are

Each of the four has its own domain; none can substitute for another. We focus on the second.

2. Its Meaning Compressed into a Single Passage

The original text of the *Yogācārabhūmi-śāstra* is extremely precise:

「諸蘊生起已，由各自緣，有各別業。彼諸所有如理觀察，瑜伽方便，是名作用道理。」 *"Once the aggregates have arisen, through their respective causes and conditions, they each have their own distinct activity. The yogic means of observing all of this in accordance with reality is called the mode of function."*

Breaking it down:

- 諸蘊生起已 (the aggregates have arisen) — these are arisen phenomena, already born; not abstract speculation about what has not yet arisen; - 由各自緣 (through their respective causes and conditions) — behind each phenomenon's function lie its own distinct causal conditions; - 有各別業 (each has its own distinct activity) — functions are therefore distinct and particular, not a vague "usefulness"; - 如理觀察的瑜伽方便 (the yogic means of observing in accordance with reality) — the act of observation itself is the instrument of practice.

3. The Four Layers of Meaning in "Function" — All Gathered into This Doctrine

"Function" (作用) is not a single meaning. The original text lays it out in four layers, and they must be kept distinct:

First layer: the respective functions of already-arisen phenomena. The most direct usage — "The eye sees forms, the ear hears sounds, the nose smells odors, the tongue tastes flavors, the body feels tangibles, the mind discerns dharmas." The eye does the eye's work, the ear does the ear's work — this is the classic demonstration of "distinct activity" (各別業).

Second layer: the efficacy of causes and conditions in "bringing about" and "accomplishing" phenomena. Another passage in the text completes the picture:

「若因、若緣，能令諸法獲得、成辦，或諸法生已，能作種種業用，是名作用道理。」 *"Whether causes or conditions, that which enables phenomena to be obtained and accomplished — or, once phenomena have arisen, enables them to perform their various activities — is called the mode of function."*

That is — we observe not only the functions of already-arisen phenomena, but also how the causes and conditions themselves that brought them forth perform their own contributory efficacy. For example: seed + sunlight + water → a sprout can grow. "The sprout can grow" is the function of the arisen phenomenon. The three conditions of seed, sunlight, and water each have their own efficacy in bringing about the result "the sprout can grow."

Third layer: distinguishing phenomena by their own activities. The text states this concretely and minutely: - The eye has seeing as its activity, the ear has hearing as its activity… up to the mind having discerning dharmas as its activity; - 地能持 (the earth element can support), 水能爛 (the water element can moisten and decompose), 火能燒 (the fire element can burn), 風能燥 (the wind element can dry) — the four great elements each have their own activity.

These are not labels imposed by humans; they are the activities intrinsic to the things themselves. Through discerning by their own activities, we are able to distinguish things that appear similar: the difference between earth and water is not "both are matter," but "one can support, the other can moisten."

Fourth layer: the efficacy of practice. The text uses the contemplation of impurity (不淨觀) as its example:

「善修、善習、多修習不淨，能斷欲貪。」 *"Skillfully cultivated, well practiced, repeatedly cultivated, the contemplation of impurity can cut off sensual craving."*

"Can cut off sensual craving" is the efficacy of the practice of contemplating impurity — but this efficacy is not an empty claim; it is because between the cultivation of the contemplation of impurity and the weakening of sensual craving there exists an observable, repeatable correspondence. This shows that "function" also includes the efficacy of the practice method itself, not only functions in the objective physical world.

4. The Key Distinction from "Mode of Validation" — The Line Contemporary Readers Most Often Blur

This point must be clarified on its own.

The mode of function asks: "What was this thing originally doing? What did this cause and condition bring about?" The mode of validation asks: "How do we know that a thesis has been established?"

The text says:

「由至教量、現量、比量證驗故，所立義得安置成立……是名證成道理。」 *"Because it is verified by scriptural authority, direct perception, and inference, the meaning to be established is set in place and established… this is called the mode of validation."*

Thus: - Fire can burn — this is the mode of function; - The causal judgment "because there is fire, there is burning" withstands examination by the three modes of valid cognition — this is the mode of validation; - Sitting too long beside a fire will cause burns — the function itself of that situation — this is the mode of function; - "This causal report about burning withstands examination" — this is the mode of validation.

Contemporary writers often say "I see X function, therefore X is established," which in logical terms has already flattened the two layers. The terminological division of this text does not permit such conflation.

5. From "Describing Functions" to a Criterion for Scrutinizing Speech

The text also turns the four modes of reasoning into a tool for judging whether a statement accords with reality:

「若所顯示宣說，不違觀待、作用、證成、法爾四道理，名為處；與此相違，名為非處。」 *"If what is shown and proclaimed does not contradict the four modes of reasoning — dependence, function, validation, and thusness — it is called 'a correct place.' What contradicts them is called 'an incorrect place.'"*

That is — any claim must be in accord with all four modes — dependence, function, validation, and thusness — to be a "correct place" for speech in accordance with reality; if it violates any one of them, it is an "incorrect place."

The mode of function therefore does not merely describe functions; it becomes a measuring stick for scrutinizing speech. A statement like "this method can cure that disease" must withstand:

- Dependence: has it taken into account the appropriate conditions? - Function: does it indeed have the capacity to produce that effect? - Validation: is there scriptural authority, direct perception, or inference to verify it? - Thusness: does it accord with the way things actually operate?

6. "Knowable Through One's Own Activity" — An Independent Route of Cognition

The text says that phenomena with form can be known through five characteristics, one of which is "knowable through one's own activity" (由自作業可得) — that is, you not only know what it looks like, but also observe what it does in order to know it.

It further says:

「若因若緣有變異故，當知果亦隨之變異。」 *"When causes and conditions undergo change, know that the results also change accordingly."*

When causes and conditions change, the results change as well — this follows the same cognitive route as the mode of function: through activity and through the changes of cause and effect, one comes to know phenomena. It is both a phenomenological description (this is how things are) and a methodological discipline (know things by observing their changes).

II. Walking Through It in Daily Life

Below, we walk the mode of function step by step through things you might encounter today. Each scenario corresponds to a layer of the original definition.

Scenario One: Morning, You Open Your Eyes

You pull open the curtains. Photons enter the eye, the photoreceptor cells on the retina convert them into electrical signals, the optic nerve transmits them to the visual cortex — you "see" the city outside the window. The eye has seeing as its activity — this is the most direct example of the activity of the six consciousnesses.

The easiest place to mis-map: we tend to read "seeing" as something at the level of consciousness / of "us," as if a subject is doing the seeing. But the structure of the mode of function is — the eye does the eye's activity, the visible form does the visible form's domain (as the object seen), and it is the convergence of these two activities that gives rise to "seeing." What we observe is the simultaneous occurrence of this pair of activities, not something accomplished by consciousness alone.

Scenario Two: Your Phone Notification Rings

The ear has hearing as its activity. The notification sound is the object, received by the ear's activity.

If you're wearing noise-cancelling headphones and don't hear it — the ear's activity was always there; it's just that the causes and conditions (the muffling of the headphones, the interruption of signal transmission) had not converged. The moment you take off the headphones or switch off the noise cancellation, the result returns. There is no need to re-"prove" that the ear can hear.

This brings out the second layer: when causes and conditions change, the result changes accordingly — activity is not an abstract, permanent self-nature; it is a manifestation of the convergence of causes and conditions.

Scenario Three: You Take a Sip of Coffee

The tongue has tasting as its activity. Coffee molecules dissolve in saliva, dock with receptors on the taste buds, nerve impulses travel upward, and you taste bitterness and aroma.

Note — what the tongue tastes is the portion of chemical information in the food that can dissolve in saliva and dock with taste-bud receptors, not the entirety of the food. The tongue's activity has a scope: it is not responsible for tasting the price of this coffee, its caffeine content, or its metabolic curve in your liver.

This is where modern people most often misread: we tend to generalize "the tongue can taste" into "the food is inherently this flavor." But the mode of function tells us — bitterness is the result of the convergence of the tongue's domain and the caffeine's domain, not the coffee bean inside a sealed laboratory declaring "I am bitter."

Scenario Four: You Lean Back in Your Chair to Think

The body has the sensation of touch as its activity. You feel the chair back supporting your lower back.

This small matter of "you are sitting in a chair" is actually two layers of distinct activities occurring simultaneously: - On your side — the body's capacity to sense touch (perceiving that support); - On the chair's side — the supportive bearing of the earth element (the chair is a solid structured object, intrinsically possessing the earth element's activity).

The two activities converge, and "you are sitting" occurs.

Scenario Five: You Argue with a Colleague and Irritation Arises

The mind has discerning dharmas as its activity. The mind is one of the six consciousnesses; its activity is discrimination, selection, and naming.

Irritation is not the mind's essential activity; it is the reaction of the mind when it strikes an obstacle in its task of "discerning." Later Chinese Buddhism elevated "the mind" very high (the mind as sovereign), but returning to this passage of the *Yogācārabhūmi-śāstra*, the mind as one of the six consciousnesses has an activity on the same level as the eye, ear, nose, tongue, and body — it is responsible for discernment at the level of consciousness; it does not presuppose "the mind is ultimate reality."

Scenario Six: You Exercise, Drink Water, Take a Shower

Here the activities of the four great elements (四大, mahābhūta) are laid out: - 地能持 (earth can support): you stand on the ground, sit in a chair, step on the treadmill; - 水能爛 (water can moisten and decompose): drinking water moistens your throat; showering dissolves the sweat; - 火能燒 (fire can burn): body temperature at 36°C, food broken down by biological enzymes in the digestive tract (approximating fire's scorching quality); - 風能燥 (wind can dry): the hair dryer dries your hair; the air conditioner removes moisture from the air.

The easiest mis-map: reading the four great elements as the periodic table of chemical elements. But what the text discusses is the level of activity — supporting, moistening, heating, drying — these four things themselves. When you observe "earth can support," you are observing a demonstration of "all things with form rely on some kind of bearing to stand," not writing a geological treatise.

Scenario Seven: You Notice "Meditation Seems to Calm Me Down"

This enters the fourth layer — the efficacy of practice.

The original text states plainly: "Skillfully cultivated, well practiced, repeatedly cultivated, the contemplation of impurity can cut off sensual craving." A contemporary version:

You have practiced mindful breathing for several months and notice that your reaction time when provoked has lengthened, and the granularity of your emotional experience has become finer.

This correspondence of "practice → change in response" is precisely the efficacy of practice, falling within the scope of observation of the mode of function.

Note the fine division of labor: - "Meditation calms me" — the observed efficacy itself — this is the mode of function; - "Meditation is worth recommending; research has verified its effects" — the thesis being verified and established — this is the mode of validation.

Many contemporary articles mix the two, so that "I feel it's somewhat useful" and "randomized controlled trials have confirmed its effectiveness" become one blob. The division of labor in this text tells us: the former is one of the materials for the latter, but is not equivalent to it.

Scenario Eight: You See an Ad for a Product

「本品可調節您的免疫力。」 *"This product can regulate your immune system."*

Run it through the four modes:

- Dependence: what conditions does immune regulation depend upon? - Function: what is this product's own activity? What does it actually do at the biochemical level? - Validation: is there clinical testing to verify this claim? - Thusness: how does the human immune system actually operate to begin with?

The "function" item forces you to ask: what is this thing's own activity, rather than listening to what it says it can do for you. A vitamin C tablet's activity is participating in collagen synthesis; a herbal extract may be some plant alkaloid acting on some receptor. Advertising rhetoric tends to skip "what is my own activity" and jump straight to "what I can do for you" — this is precisely what the mode of function demands we see clearly.

III. Why Contemporary People Need It

1. The Word "Function" Has Been Washed Too Pale

In contemporary usage, "function," "activity," "efficacy," and "use" are nearly synonyms. But in the *Yogācārabhūmi-śāstra* they are divided with great precision:

- 功能 (function, activity) = what this thing itself does - 功效 (efficacy) = what something achieves in you (the accomplished result) - 用處 (use) = what you use it for (subjective purpose)

Commercial rhetoric almost exclusively speaks of the latter two, and smuggles "function" into "what use is it to us." One of the contemporary meanings of the mode of function is precisely to peel "what it itself does" back out of the rhetoric of "what use is it to us."

2. In the AI Era, the Discernment of "Distinct Activities" Becomes Important Again

Large language models, recommendation algorithms, automated systems — they are all tools with strong capabilities but narrow activities. A model can write fluent text, but its activity is not "understanding"; an algorithm can give you personalized recommendations, but its activity is not "caring about you."

The discipline of the mode of function is: - What it can do (its proper task, in the manner of "the eye has seeing as its activity"); - What it cannot do (it has no mysterious activity beyond the eye, ear, nose, tongue, body, and mind — no other magical function).

This is also where contemporary people most easily mis-map — intimidated by its impressive capabilities, we read its function as broader than it actually is. The mode of function is a foolproof mechanism against over-attribution.

3. Distinguishing "Looking at Function" from "Being Verified," Protecting Our Judgmental Rhythm

In the flood of information, what we most often get wrong:

- Treating "someone says it works" as "it works" (skipping verification); - Treating "I feel it works" as "it works" (skipping verification); - Treating "I can't see that it works" as "it doesn't work" (skipping observation).

The division in the *Yogācārabhūmi-śāstra*: - Mode of function = honestly looking: "What was it originally doing?" (observation) - Mode of validation = honestly verifying: "How do we determine that this seeing is correct?" (verification)

Each has its place; neither can substitute for the other. Contemporary people live in haste and often take "I feel it's useful" as the conclusion — this misses an entire step. The mode of function requires first observing the activity clearly, then entering the procedure of validation.

4. When Facing Practice Methods, Avoiding "I Only Trust What Research Has Shown"

At the other end stands the research-oriented person — only accepting RCTs, neuroimaging, statistical significance; without these, refusing to touch any practice method.

But the mode of function has a position reserved specifically for practice: "Skillfully cultivated, well practiced, repeatedly cultivated, can cut off sensual craving." The force of this statement does not lie in whether it has a double-blind experiment; it lies in the fact that it is an observation that the act of practice itself has an efficacy that can be experienced.

If contemporary people look only at the mode of validation, they will miss this thread; if they look only at the mode of function, they will mistake "self-perceived usefulness is enough." Viewing all four modes together is what is complete.

5. It Helps Distinguish "What Makes No Sense"

"Not contradicting the four modes is called a correct place; contradicting them is called an incorrect place" — this is using the four modes as a criterion for scrutinizing speech.

A contemporary version: - A dietary recommendation that does not contradict dependence (does not assume instant effects), does not contradict function (does not attribute to food an activity it never had), does not contradict validation (has a basis that withstands examination), and does not contradict thusness (does not conflict with known physiology) — this is a "correct place"; - Conversely, "eating X cures cancer," "meditation cures all diseases," "moving objects with the mind" and the like will break on one of the criteria.

The mode of function, as one of these four measures, is often the first one that proves useful — asking "does it really, itself, have this activity?" alone can filter out a large amount of noise.

IV. Common Misreadings and Clarifications

Misreading ①: The Mode of Function = The Mode of Causality

Many readers see the word "function" and stuff the entire causal framework into it.

Clarification: Causality can be observed through multiple modes — - The mode of dependence: the conditional relationships established through dependence; - The mode of thusness: the constancy of phenomena as they are (e.g., seed giving rise to sprout is constant); - The mode of function: the respective activities of already-arisen phenomena and the efficacy of causes and conditions in bringing about results.

The mode of function is responsible only for "the functions of each phenomenon" and "the contributory efficacy of causes and conditions" — it is not equivalent to all of causality.

Misreading ②: The Mode of Function = The Mode of Validation

Modern writers often write "the function X of something has been confirmed by research." This sentence simultaneously activates the mode of function (function X itself) and the mode of validation (confirmed by research) — the two are not the same thing.

Clarification: - Function = what a thing does; - Validation = how I determine that what I am saying is correct.

One is the object of observation, the other is the ground for establishing the observation. The terminological division of this text is strict; they should not be merged.

Misreading ③: The Mode of Function = "Everything Has Its Use"

The most secularized version.

Clarification: The mode of function is not an inspirational motto; it is the wisdom of discerning differences. "The eye has seeing as its activity" is not the vague statement "the eye is useful," but rather "the eye does the task of seeing" — this is particular, precisely specifiable. "A bowl of soup is nourishing" is not at the level of the mode of function; "after entering the stomach, the protein in the soup is broken down into amino acids" is a description at the level of the mode of function (though this layer too can be further subdivided).

Misreading ④: Reading the Mode of Function as Physics or Functionalist Philosophy

It sounds close to "functionalism" in philosophy (the mind reducible to functional organization), and also close to physics' descriptions of system function.

Clarification: - Physics describes externally measurable causal mechanisms; the "activity" in the mode of function is, from the perspective of the yogic observer, the reality-accordant discernment of the functions intrinsic to phenomena; - Functionalism claims the mind just is functional organization; the mode of function does not presuppose this metaphysical position — it merely observes the distinctions of activities; - The two use similar words but have different connotations. Replacing the Yogācāra concept of activity with physics or functionalism would lose the dimension of "the yogic means of observing in accordance with reality" — namely, that it is originally an instrument of practice, not a proposition of epistemology.

Misreading ⑤: The Mode of Function Encourages Instrumental Rationality

Reading "each thing does what it can do" as "people should instrumentally use everything."

Clarification: The mode of function does not advocate treating everything as a tool. It advocates discerning differences — not conflating, not exaggerating, not omitting. When you see clearly that the eye, ear, nose, tongue, body, and mind each do their own work, what you gain is not "a person should be decomposed into tools," but rather "a person (including me) is not a single-function thing — I have eye, ear, nose, tongue, body, and mind each with their own activities, and they are often in disharmony with one another — this is precisely one of the structures of my affliction."

This is also one of its paths toward liberation: seeing the differences in the distinct activities of the aggregates is the beginning of seeing through "I" as a single, constant subject.

Misreading ⑥: Reading "Efficacy of Practice" as "Miraculous Instant Results"

The contemplation of impurity can cut off sensual craving — that is the efficacy of practice, but this does not mean "sit once and you become a Buddha on the spot."

Clarification: Efficacy is the result of accumulated cultivation and maturing conditions. The original text deliberately uses three repetitions — skillfully cultivated, well practiced, repeatedly cultivated (a deliberately emphasized rhythm) — not a matter of one day or one month. Contemporary people who want to cure a lifetime of anxiety with a single meditation session are compressing the concept of "efficacy" into "instant results."

Misreading ⑦: Ignoring the Message of "Change in Causes and Conditions"

"When causes and conditions undergo change, know that the results also change accordingly" — this is not merely a physical statement; it reminds us that activity is a manifestation of the convergence of causes and conditions, not an isolated, permanent self-nature.

Clarification: When you observe a function disappearing (e.g., eyes looking at the phone until they are sore and blurry), the mode of function tells you this is not the ontological label of "my eyes are broken", but rather that causes and conditions have changed — the light is too dim, the characters too small, the duration too long, the tear reflex suppressed. Find the causes and conditions, adjust the causes and conditions, and the function returns. This is closer to the facts than self-labeling like "I have an eye disease" or "my eyes are bad," and it points more directly toward a solution.

Conclusion: The Place of the Mode of Function

The four modes are four perspectives from which a yogic practitioner observes the world. In their midst, the mode of function occupies a position that connects what comes before and after:

- It is closer to concrete particularities than the mode of dependence (the functions of already-arisen phenomena); - It provides the material for verification to the mode of validation (function is the "what" of "what is being verified"); - It is the mode of thusness unfolding in concrete matters (activity is one manifestation of thusness).

Its most distinctive sentence is:

由自作業可得。 *"Knowable through one's own activity."*

This means — without relying on others' introductions, others' evaluations, or others' views of me, I can also, from the observation of "what I do, what I can bring about," come to know "this particular thing's being here, in this place." This is an autonomous, fact-seeking form of cognition. Placed in the contemporary context, it is:

Not held hostage by definitions, not held hostage by fashionable discourse — returning to the fact of "what this thing was originally doing," and beginning observation from here.

The mode of function does not ask us to become functionalists, nor does it ask us to reject all symbolism and meaning. It simply, among the many dimensions of observation, gently turns our gaze back to —

This thing, that item — each does its own work; this dharma, that condition — each brings about what it can bring about.

Seeing this clearly is where the work begins.