How Do Sense Faculties Become Internal Āyatana?

September 8, 2019; last revised December 12, 2024

Indriya and Āyatana

1. Sense faculties are a crucial concept in Buddha Dhamma. The six sensory faculties are the eyes (cakkhu), ears (sōta), nose (ghāna), tongue (jivhā), body (kāya), and mind (manō).

Those are also “internal rupa” created by kammic energy. With those, an average person experiences the outside world AND forms attachments to them.
The sensory faculties of an average human are “indriya.” They become “internal āyatana“ only if we use them with raga, dosa, or moha.
When an “indriya“ becomes “internal āyatana,” it does not grasp an accurate representation of an external rūpa (sights, sounds, tastes, smells, touches, and memories). Thus, the mind experiences a “distorted version” of a given rupa. That “distorted version” of a given rupa is called an “external āyatana“ (for example, “my house,” “my friend,” etc.); see “Contact Between Āyatana Leads to Vipāka Viññāna.” Therefore, an external āyatana is a “distorted version” of a given external rūpa. That is why one attaches to it. For an Arahant, external rupās never become external āyatana; they are just external rupās.
Note that an “external āyatana” arises in the mind. It is NOT the external rupa.
There is no equivalent English word for āyatana, so we will keep using indriya and āyatana from now on.

2. An Arahant has removed all greed, anger, and ignorance from the mind; it is better expressed by saying all anusaya and samyojana (the ability to generate greed, anger, and ignorance) have been removed. The sense faculties of an Arahant are indriya. With his sensory faculties, an Arahant experiences “external rūpa“ such as “a house,” “a taste,” etc., without any attachment. That house may be an elegant house where he lived some time back. But now it is just a house. That person could have been a “close friend” then, but now just another human being. Of course, the Arahant will recognize the house he lived in as a child and that the person was his friend.

In brief, a sense faculty is an indriya if there is no “attachment.” It becomes an internal āyatana if one is attracted to or repulsed by using it. In the same way, an external rūpa becomes an external āyatana if one becomes attached to it.
The Pāli word for attachment is “taṇhā.” It is critical to realize that “attachment” can occur via greed, anger, or ignorance. Once “attached,” one just keeps thinking about it (that means generating abhisaṅkhāra; see below). Also, see “Tanhā – How We Attach Via Greed, Hate, and Ignorance.”

How Do Indriya Become Internal Āyatana?

3. First, let us clarify the difference between an internal āyatana and an indriya.

Our initial sensory inputs (what we see, hear, etc.) are due to kamma vipāka. It is unnecessary (or even possible) to understand that kamma vipāka arises due to past kamma. We only need to know how such kamma vipāka can lead to new kamma formation; that is what propagates suffering to the future.
At initial sensory contact, such sensory faculties operate as indriya. For example, when we see an attractive person on the road, we just “see a person” with the cakkhu indriya. This is like taking a picture with a camera; the picture registers in mind.

4. However, based on that initial sensory experience, we may INTENTIONALLY use those indriya to enjoy that sensory experience repeatedly. Then those indriya become āyatana. In the above example, if we get attached to that attractive person and keep looking at that person, we will be using our eyes as cakkhāyatana (cakkhu āyatana rhymes as cakkhāyatana.)

Therefore, an initial sensory event is captured by an indriya. But immediately after receiving that sensory input, a puthujjana uses that sense faculty as an internal āyatana. That happens if we get attached or form “taṇhā“; see #2 above.
It is only when one attaches to what is seen that it becomes cakkhuāyatana or cakkhāyatana. Thus, an Arahant has cakkhu indriya, but it will not become cakkhāyatana.

5. Let us take the example of two people eating a delicious cake. One is an average human (X), and the other is an Arahant. Here, the sense faculty is taste (jivhā).

Both will generate the same kind of jivhā viññāna when they first taste it. That is just the taste of the cake. If the sensory elements in the tongue and the brain work normally, both will likely find that cake “tasty.” That “good taste” is a kamma vipāka. (An infinite number of kamma bīja are waiting to bear fruit, including such a “small vipāka” as tasting a piece of cake.)
The difference becomes apparent just after tasting the cake. The Arahant would forget all about that taste, even though he/she would have felt the “good taste.” It was just a sensory experience; thus, the Arahant used that sense faculty as an indriya.
On the other hand, X may “fall in love” with that tasty cake. She may ask for another serving. Now, she is using that sense faculty as a āyatana. She will accumulate new kamma with such actions.

How One Indriya Can Lead to Many Āyatana (Salāyatana)

6. When we experience a sensory event due to one indriya, we may use some or all of the indriya as āyatana. Then, the set of indriya becomes salāyatana.

In the above example of a tasty cake (a kamma vipāka for both), they experience “a tasty cake.” While the Arahant will not have any more thoughts about that taste, the average human (X) may be just getting started. She may ask for another piece even if she is not hungry.
Let us analyze the situation carefully. The Arahant may accept a second piece if he is hungry. That request was not made because of greedy thoughts. Thus, jivhā indriya (tongue, nerves, etc., and the jivhā pasāda) has NOT led to the arising of jivhā āyatana. The arising of an āyatana is a mental construct.
If X asks for another piece, even if she is not hungry, that is definitely due to a craving for that taste. Then, her tongue has become a āyatana. Her request could be based on BOTH hunger and craving (if she is hungry.) So, now her tongue (more precisely jivhā pasāda) is still a āyatana.

7. Whether or not X’s jivhā pasāda rūpa (internal indriya for tasting) has become a āyatana may become more apparent if she takes further action.

She may smell it and say, “It smells good too.” She may keep saying how good the taste is and ask about the recipe or where to buy one.
Now, she is using her sensory faculties as āyatana. Ghāna pasāda rūpa (for smelling) has now become ghānāyatana (ghāna + āyatana). Eating cake is not limited to quenching hunger; many sensory faculties are used for pleasure. “Indriya to āyatana” is a “mental transition.”
She is thinking about how to taste that cake again. Therefore, the mind (mana) has become manāyatana (mana + āyatana). If she starts writing down the recipe, her physical body (kāya) helps out, too, acting as a kāyāyatana (kāya + āyatana).
Therefore, when more than one āyatana becomes engaged, the set of āyatana (called salāyatana) may come into play. But it all started with just one sensory input, in this case, eating a piece of cake.

Indriya Become Āyatana With (Abhi)sankhāra

7. The easiest way to determine whether an indriya has become an āyatana is to check whether one has started generating greedy, dislike, or ignorant CONSCIOUS thoughts about that sensory input or experience.

Interest in a sensory input leads to attachment via greed, revulsion, or ignorance.
For example, the smell of good perfume can lead to thoughts about buying it. Seeing an enemy may generate angry thoughts. In some situations, one may get confused about what to do and make the wrong decisions.
Such CONSCIOUS thoughts are vaci and kāya saṅkhāra.
Vaci saṅkhāra are “talking to oneself” and possibly speaking too. First, greedy/angry/ignorant thoughts are generated, which may lead to speaking out (lying, gossiping, etc.).
Kāya saṅkhāra involves bodily actions, such as hitting, stealing, killing, etc. Here, one would use more āyatana since one would need to look and hear in addition to moving body parts.

8. we often use our sensory faculties as indriya: we see, hear, etc., many things in a day but ignore most of them. But when we experience something we crave, we start using our sense faculties as āyatana.

The Akusala-Mula Paṭicca Samuppāda cycle operates only when we use our sense faculties as āyatana.
Those saṅkhāra (abhisaṅkhāra) do not arise in an Arahant. That is because such saṅkhāra arise due to avijjā, i.e., they arise via “avijjā paccayā saṅkhāra.” Even though it is normally written for brevity that way, it really is “avijjā paccayā abhisaṅkhāra.”
An Arahant ALWAYS uses his/her sensory faculties as indriyās. He/she will see, hear, etc., just like an average human, but will not get “attached to” anything.

Abhisaṅkhāra Are Sankhāra With Raga, Dosa, Moha

9. Any action, speech, or thought that involves abhisaṅkhāra will turn indriya to āyatana. Just eating a cake does not involve abhisaṅkhāra, but having greedy thoughts about it does; see, “Kāma Guna, Kāma, Kāma Rāga, Kāmaccanda.”

The distinction between saṅkhāra and abhisaṅkhāra is clear-cut when those conscious thoughts (and therefore speech and actions) become immoral.
Generating thoughts of anger in a person is abhisaṅkhāra. Then, telling a lie about that person is also abhisaṅkhāra. Both are vaci kamma done with vaci (abhi)saṅkhāra.
Stealing something or hitting someone is a kāya kamma done with kāya (abhi)saṅkhāra.
Therefore, immoral thoughts, speech, and actions are based on abhisaṅkhāra. They are apuññābhisaṅkhāra (apuñña + abhi + saṅkhāra) or immoral strong saṅkhāra.

10. We can get some insights by analyzing the case of a young person (Z) becoming an alcoholic due to an association with bad friends. As a child, Z may see a bottle of alcohol and would not generate any second thoughts about it. It would just be a “seeing event,” and Z would only use his eyes (or more precisely, cakkhu pasāda rūpa) as cakkhu indriya.

But Z had some bad friends, and they persuaded him to start drinking. He has now become an alcoholic. If he sees a bottle of alcohol now, he immediately thinks about having a drink. Of course, he would have a drink If he was at a party. If he is at home, and the bottle belongs to his father, he may steal a drink from it.
It could get even worse. He may be drinking at a party and may get into an argument with someone. Suppose that leads to a fight, and he kills that person. He may get the death sentence or go to jail for a long time. But a much worse outcome awaits him at his death. He would be born in an apāya.
I hope you can see that vaci and kāya abhiaṅkhāra are behind all those. They are defiled/immoral saṅkhāra. They are thus abhisaṅkhāra. If he kills someone, that is due to an apuññābhisaṅkhāra (apuñña abhisaṅkhāra). That would qualify him to be born in an apāya.

11. There are also puññābhisaṅkhāra (puñña + abhi + saṅkhāra) or strong moral saṅkhāra.

For example, feeding a hungry person or giving to charity are kāya kamma done with strong kāya saṅkhāra. They are both puññābhisaṅkhāra.
Such strong puñña kamma done with puññābhisaṅkhāra lead to good rebirths (in human and higher realms).

How Do External Rupā Become External Āyatana?

12. When an indriya becomes an internal āyatana, the corresponding external rūpa becomes an external āyatana.

Let us consider the following example. You are walking down a street and see a person approaching you at a distance. Without recognizing who it is, your eyes are working only as indriya. But as the person gets closer, you recognize him as one of your friends. At that moment, your cakkhu indriya has become a cakkhāyatana. At the same time, that external rūpa of a “person” has now become a “friend.”
To take that one step further, suppose after some time you get into an argument with that friend, and it escalates to the point that he has become an enemy. Now, if you see him on the road, you will recognize him as an enemy. When you see him, your cakkhu indriya will again become an internal āyatana, and the body you see will become an external āyatana.
However, those two external āyatanās are very different. In one case, you saw a friend and, in the other, an enemy, even though that external rūpa (body of that other person) was the same.

13. We can find many examples in our daily lives to see how an indriya becomes an āyatana. In another example, suppose you park the car on the side of the road and go to a restaurant to eat. When you come back, you see that someone has bumped his car into it, and there is a scratch on it. You, of course, get upset.

Suppose, after a while, you sell that car. Then, a few days later, you see it was destroyed in an accident. But now you are not upset about the same car getting wrecked. Your cakkhu indriya does not become an internal āyatana when you see that badly damaged vehicle. The external rūpa (the seeing of the car) does not become an external āyatana.
The only difference was that you had given up your attachment to that car the moment you sold it. It is no longer “your car.” It became just another car the moment you gave up ownership.

How to Stop Indriya Becoming Āyatana?

14. That last example illustrates how one ends suffering at Arahanthood. When one no longer attaches to ANYTHING in this world, one’s mind will not be perturbed by anything. That includes knowing that one day, one’s own body will die.

However, the state of mind of an Arahant cannot even be comprehended by an average human. It is a long process to go from being an average human to becoming an Arahant.
We must follow the path step-by-step. Attachments to “worldly things” CANNOT be forcefully removed from one’s mind. The first step is comprehending the unfruitfulness and danger of doing IMMORAL things to get sensory enjoyment. See “Is It Necessary for a Buddhist to Eliminate Sensual Desires?“
However, initially, it is good to get an overview of the “big picture” or the fundamentals of Buddha Dhamma. That is necessary to discard the wrong views about this world, including kamma and kamma vipāka, and the validity of the rebirth process. One cannot even start on the Noble Eightfold Path with wrong views about such fundamental concepts.
This series on “Origins of Life” is so important. One must evaluate all existing views (which we summarized in the early posts in this series). The Buddhist view is more complex and will take several more posts to complete.