Indian wisdom on Ocular Perception and Cognition - Satyam Dwivedi
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Indian wisdom on Ocular Perception and Cognition

Indian wisdom on Ocular Perception and Cognition


Perception plays a significant role in our day to day life. Indian philosophical schools have given different accounts of perception. Based on the different types of perceptions the process of perception also varies from school to school. In spite of spiritual motive and liberation being the key objective behind perception theories, the detail given is quite technical and scientific.

Ocular perception, being the primary and the most used perception is given the utmost importance. The process of ocular perception is described with an exhaustive technical account in various schools under Indian Philosophical tradition.

This paper is an attempt to provide an account of ocular perception in Indian philosophical tradition along with its comparative study with the modern science.



1 Introduction

Attaining the valid knowledge has been the concern of Indian philosophers since antiquity. The reason for that is the belief that valid knowledge leads to liberation, whereas, the invalid or false knowledge is the root cause of all sufferings and bondages.

There are three widely accepted sources of valid knowledge:

  1. Perception,
  2. Inference, and
  3. Testimony.

Inference and testimony are the secondary sources of knowledge, whereas, the perception, being based on the direct input from sensory organs is considered the primary source of knowledge. Perception being the most used and primary tool for valid knowledge is given prime importance and validity in various schools. Amongst various kinds of perceptions also the ocular perception is used primarily due to its frequent and foremost use.


2 Trivia

Indian philosophical schools have never been rigid about their ideas, and only the ideas which can be proven by arguments are given a place. The only thing they care about it the valid knowledge. That’s why this is explicitly mentioned:

‘Yuktiyuktaṃ vacō grāhyaṃ bālādapi śukādapi,

Ayuktamapi na grāhyaṃ sākṣādapi bṛhaspatēḥ.’ (Bhāskarācārya)

One should cognize valid thoughts even if they are from a child or a parrot, and should not cognize the thoughts devoid of arguments even if they are from most knowledgeable of people. Following the same, from time to time old concepts are refined by the philosophers as and when required. That is why the scholars of different schools participated in healthy debates with the experts of other schools to argue and reach to the universally valid and acceptable ideas.


2.1 Sense organs & Perception

Just like the perception is given the supreme importance in day to day life, philosophers also give it the same credibility. In fact, there are many philosophers, who have not taken inference as a valid tool for cognition. Even though there may seem a conceptual difference in the process of cognition through perception between various philosophical schools, it is accepted by all as a valid tool for cognition.

Sense organs and their functionalities are the fundamental elements of the theory of perception.  A general query may arise that why can’t we perceive sense objects such as taste and smell from eyes? The thing is that the eyes are the first sense objects to be born out of the matter that holds the property of visual consciousness. And according to the philosophy, a sense organ can perceive only specific sense objects, and not all types of sense objects as all sense organs are born/related to the matter of respective properties. Eyes in the nyāya philosophy are proven to be taijasa with the help of inference.


3 Ocular Perception

The process of ocular perception requires these key elements:

  • Cakṣu
  • Cakṣu Raśmi
  • Dravya
  • Sannikarṣa

In the process of ocular perception, the rays travel from the eyes to the object to provide an idea about it, only then we are able to perceive something. This theory with slight variations is widely accepted by the western philosophers as well. Cakṣu Raśmi and Nayana Raśmi are proven with the help of various arguments in the Nyāya Darśana 3.1.32-3.1.43. Here are a few arguments:

‘Naktaṃcaranayana-raśmidarśanācca’ (Nyāyasūtra, 3.1.43). Here, by sighting rays in the eyes of the creatures wandering in the night, such as cats, it is inferred that human beings too have them in their eyes. This is how it is inferred: ‘Asmadādicakṣuḥ raśmiviśiṣṭaṃ cakṣuṣṭatvāt mārjāracakṣuvat’ (Prasannapadā ṭīkā on Nyāyasūtra, 3.1.43). Our eyes have rays just like the cats. Here also it is claimed that the light rays travel to the object for its perception- ‘Raśmyarthasaṃnikarṣaviśēṣāt tadagrahaṇam’ (Nyāyasūtra, 3.1.32).

The author of Nyāyakandalī has also accepted the same thing: ‘Raśmyarthasaṃnikarṣādanubhūt-rūpasparśa nāyanā raśmayō dūrē gatvā saṃtamartha grahṇanti’ (Nyāyakaṃdalī Sādharmya Prakaraṇa). In Vēdāṃta philosophy as well, the travel of rays is accepted: ‘Tatra ghrāṇarasana-tvagindriyāṇi svasthānasthitānyēva gandharasa-sparśōpalambhānjanayanti. cakṣuḥśrōtē tu svata ēva viṣaya dēśaṃ gatvā svasvaviṣayaṃ grahnītaḥ’ (Vēdāṃta Paribhāṣā), which means that the sense organs of smell, taste and touch make perception possible staying at their places only, whereas, for vision and audition, the respective sense objects need to come in contact with the object for its perception.


3.1 The simultaneity illusion

Nyāya darśana gives a very scientific account of light rays travelling from eyes, in which Naiyāyikas refute the premises of other arguments and establish their theory: ‘Yad gacchati tat sannihitavyavahitārthau kramēṇa prāpnōti. tatkathaṃ śākhācandramasōstulyakālōpalabdhiḥ’(Nyāyakaṃdalī). Here the Pūrvapakṣī raises the query that if rays travel from eyes, come in contact with the object and then perception takes place, then how the simultaneous cognition of a branch and the moon is possible? As the distance between the moon and the branch is quite a lot. So, based on this argument the rays will reach the branch first, perceive it and its cognition will take place. Afterwards, the rays will reach the far-far distant object moon, and the cognition will take place. There should be some delay in the process. However, the perception is simultaneous in practice.

The Naiyāyikas then address the query explaining: ‘Indriyavṛttērāśusaṃcāritatvāt palāśaśatavyatibhēdavatkramāgrahaṇanimittō’yaṃ bhramō, na tu vāstavaṃ yōgapadyam’ (Nyāyakaṃdalī). What you say is true. The perception of the moon takes place only after the perception of the branch, however, the event takes place so fast that we feel both of the perceptions to be simultaneous. To prove the whole process, the Śatapatrabhēdanyāya experiment was performed.

‘Uparyuparisthitiśatasaṃkhyakapatrāṇāṃ sūcyā yugapad bhēda- bhramaviṣayāṇāmapivastuta ēkabhēdānantaramaparabhēdaḥ’ (Māthurī ṭīkā on tatvaciṃtāmaṇi).

In this experiment, a hundred lotus leaves were placed together, one on the top of another one. When they are pierced with a needle, it feels like all of the leaves were pierced simultaneously. However, if we ponder over it, we can conclude that the needle pierces through each leave one by one before piercing the last leave. The process of piercing is so fast that we can’t feel the difference of time. In the same way, the simultaneous perception of the branch and the moon takes place.

There is another example for this simultaneous cognition in Nyāyasiddhānta Muktāvalī:

‘Tulyakālagrahaṇaṃ cāsiddhamēva, tadabhimānasya kālasannikarṣērṇavōpapattēḥ. acintyō hi tējasō lāghavātiśayēna vēgatiśayaḥ, yat prācīnācala- cūḍāvilambinyēva bhagavati mayūkhamālini bhanōdarēṣvālōka ityabhimānō lōkānām. (Muktāvalī, Pratyakṣa khaṇḍa)’

Which means that when the sun rays travel to our house, as soon as the sun rises in the east, only then we perceive and cognize that the sun has risen. Here the process of the rays coming to our house, their availability and the perception of sunrise happens simultaneously. The reason behind it is the fast speed of light. It can be proven by arguments that the process of sunrise and its rays reaching earth is a sequential process and not a simultaneous one.

According to the modern science, the speed of the light is 2,99,792 km/s. In fact, light is the fastest of all things. The distance between the sun and the earth is 149.6 million km. It takes around 8 minutes and 20 seconds on an average for the sunlight to reach the earth, and the whole process is sequential. This way we can say that in spite of the availability of fewer resources back then, the concept of sequential processing in Nyāya darśana is scientific.


3.1 Perception of external objects

A condition is equally applicable to all sense that they are able to cognize an object only when it comes in any kind of contact with them, ‘Iṃdriyāṇi vastuprāya prakāśakārīṇi jñānakāraṇatvādālōkavat’ (Tarkabhāṣā). An inference is given in Tarka Bhāṣā as well to support it: ‘Cakṣuḥśrōtē vastuprāya prakāśakārīṇi jñānakāraṇatvādālōkavat’ (Tarkabhāṣā). It means that eyes also facilitate perception through contact with an object. This concept of Nyāya philosophy is contradictory to the Bauddha philosophy. According to the Bauddha belief, the eyes facilitates cognition without contact with the object, as eyes cognize only those objects which are distant and not at all in contact. They give the example of Kājala (led) and argue that why it is not cognizable even after being in the closet proximity and direct contact if eyes can cognize the objects which come in contact?

‘Cakṣuḥśrōtēmanō’prāptaviṣayam- tathā hi dūrāt rūpaṃ paśyati, akṣisthamanjanaṃ na paśyati. (Abhidharmakōśa, 1043)

The Naiyāyikas then give the example of magnate to resolve the query. ‘Yadyaprāptaviṣayaṃ cakṣuḥ kasmānna sarvamaprāptaṃ paśyati, dūraṃ tiraskṛtaṃca. kathaṃ tāvadayaskāntō na sarvamaprāptamayaḥ karṣati. prāptaviṣayatvē’pi caitat samānam’ (svōpajñabhāṣya on abhidharmakōśa, 1.4.3). Just like a magnet attracts pieces of iron from a distance without coming in contact, the eyes perceive the things situated at a distance. The magnet is unable to attract iron pieces situated very distant. Likewise, the eyes also can’t perceive the things situated very distant or in very close proximity:

Sage Gautam gives a detailed account of ocular perception. ‘Indriyārthasaṃnikarṣōtpannaṃ jñānamavyapadēśyamavyabhicāri vyavasāyātmakaṃ pratyakṣam’ (Nyāyasūtra, 1.1.4), which means that the unsaid (not told/referred earlier), flawless and decisive knowledge resulting due to the six types of saṃnikarṣa such as saṃyoga of sense organs with an object is known as perception.

According to Nyāya, a substance can come in contact with other substances by saṃyoga relation. There are twenty-four properties such as the form in dravya (substance) and various universals such as form-hood in form by samavāya (inheritance) relation. For the perception of pot substance, saṃyōga sambaṃdha (contact) between the light rays of the eyes and the substance takes place.

The perception of an object happens when there is saṃyōga sambaṃdha between the object and the rays that travel from eyes. There are two opinions about it. The first version says that the rays travel from the eyes to the locus of the object, and make perception possible by taking the form of the object. The other version says that the rays from the eyes return after adapting the form of the object, and the perception then happens in the bulbus oculi. Whereas according to the Sāṃkhya philosophy, after the indriya praṇālikā has grasped an object, a vṛtti of the same dimension gets formed in citra and buddhi, this is perception. ‘Indriya praṇālikayā cittasya bāhyavastūparāgāt tadviṣayā sāmānya-viśēṣātmanōarthasya viṣēśāvadhāraṇapradhānā cittavṛttiḥ pratyakṣaṃ pramāṇam. lamaviśiṣṭaḥ pauruṣēyaścittvṛttibōdhaḥ. (Yōgadarśana Vyāsabhāṣya, 1.7)

If we go a bit into detail, Nyāya philosophy accepts only bulbus oculi as cakṣurindriya.  ‘Rūpōpalabdhasādhanamindiyaṃ cakṣuḥ kṛṣṇatārāgravarti’(Tarkabhāṣā). Since its a product of light, so the rays get birth from here only and come in contact with the objects outside, ‘Śarīrasaṃyuktaṃ jñānakāraṇamatīndriyaṃ indriyam’(Tarkabhāṣā). As a matter of fact, cakṣurindriya as well is atīndriya (invisible) like other sense organs.

Sāṃkhya darśana, with a few variations, accepts the cakṣurindriya with same features. However, the emphasis is on praṇālikā as opposed to indriya in Nyāya. According to them, it is the hole in the iris, which is also known as kanīnikā or pupil in modern science. The rays come in contact with the objects coming out of it only. Their account for the process of perception is also fascinating, ‘Cakṣurindriyārthapātisannikarṣōtpannaṃ jñānaṃ cākṣuṣaṃ pratyakṣam’, which means that at first the cakṣurindriya travels to the locus of the object and adapt the form of the object, afterwards the cognition occurs by the saṃyōga sannikarṣa with the rays reflected from there.

Diagram 3.1: Perception of an external object

According to Nyāya philosophy, the process of perception of ghat substance is multifold. There are various types of sannikarṣa involved in the perception of a ghat. The reason behind it is that one relation can help perceive only one object, whereas, when we cognize a substance, we cognize dravya (substance), dravya rūpa (the form of the substance) and rūpatva jāti (the universal of the form-hood). Therefore, the perception of substance happens through the saṃyōga relation between the light rays from eyes and the pot, the perception of the form of the pot happens through saṃyukta-samavāya (inheritance in the object), and the perception of universal of form-hood happens through saṃyukta-samavēta-samavāya (the inheritance in what is inherent in conjoined).


3.3 Perception of reflection

Perception of a reflection is also explained in various philosophical schools. In this process, the rays from eyes travel to the mirror, get reflected and come in contact with the real-world object, only then the shadow is perceived. For example, in the process of perceiving the reflection of one’s face in the mirror, the light rays from eyes will reach the mirror, reflect, and will come in contact with the real-world face. The face will be perceived after that only.

This is described in great details in Nyāya philosophy:

Yathādarśa pratihatasya parāvṛttasya nayanaraśmēḥ svēna mukhēna saṃnikarṣē sati svamukhō pratibimba grahaṇākhyam ādarśarūpānugrahāt tannimittaṃ bhavati’ (Commentory on nyāyasūtra, 3.1.49). And also:

‘Ādarśōpari pratighātēna paravṛttō nayanaraśmirgrīvāsthamēva svamukhaṃ grahnāti, tadēva pratibimb-grahaṇamityucyatē’ (Prasannapadā ṭīkā, 3.1.49).

This opinion is based on empirical findings. An object can not exist in a locus where there is no matter available required for its creation. The perception of a pot happens as the matter required for its creation is available outside, as a result, it is present outside. However, the matter required for the creation of a face is not present in the mirror, that’s a mere reflection. Therefore, the perception will take place only in the locus of the object, which is the real world face.

There is a particular term used for it in philosophical schools: ‘alīka’, which means ‘not true’, ‘Bimba ēva pratibimbaḥ. kēvalaṃ tatrōpādhisannidhānēna anyatvaṃ darpaṇādyaantargatatavaṃ ca bhāsatē. na tu bimbāt pratibimbasya pṛthagastitvam. (Description of Brahmasūtra)’

Diagram 3.2: Perception of a reflection


This is further clarified by the examples of reflection of Sun in a pot. This reflection is asata (not true), as it holds the properties of another object. Its size gets decreased and increased based on the pot’s size, and it starts trembling when the water inside the pot trembles. In reality, these are not the properties of Sun. Therefore, the reflection of Sun is asata as it follows the properties of water: ‘Jalagataṃ hi sūryapratibimbaṃ jalavṛddhau vardhatē, jalahrāsē hrasati… ityēvaṃ jaladharmānuyāyi bhavati. Na tu paramārthataḥ sūryasya tathātvamasti’(Śāṃkarabhāṣya on Brahmasūtra)

In Bauddha Darśana as well, the substances which hold the properties of other substance are accepted as false:‘Yadanyasannidhānēna dṛṣṭaṃ na tadabhāvataḥ, pratibimbasamē tasmin vastūni satyatā katham’ (Bōdhicaryāvatāra, 9.145).

In Upaniṣadas, it is falsified giving the example of water and moon. ‘Éka ēva hi bhūtātmā bhūtē bhūtē vyavasthitaḥ, ēkadhā bahudhā caiva dṛśyatē jalacandravat’ (Brahmabindūpaniṣat, 3.1). Which means that the Moon is one, however, based on the locus of its reflection, which is water in different containers, in this case, it feels different.

The chief contrast we can notice here from modern science is that the light rays from eyes fall on the mirror according to the different philosophical schools, whereas, according to the contemporary science the sun rays get reflected from face to the mirror. However, both of them consider the reflection asata (not true).


4 Conclusion

The difference between the modern science and Indian philosophical schools in terms of ocular perception for cognition are evident. However, the scientificity of most of the arguments and their relevance till date is unquestionable. This paper presented a bird’s eye view; therefore, a detailed study in this regard may be helpful to bridge the gap.


4.1 Limitations and future work

An overview and reference of other types of perceptions are given wherever required; however, this paper is strictly focused on ocular perception. There are various types of perceptions other than ocular perception, a comparative study of them will prove itself a milestone in this area.



  • Commentary on Nyāyasūtra, 3.1.49
  • Description of Brahmasūtra
  • Abhidharmakōśa, 1043
  • Brahmabindūpaniṣat, 3.1
  • Bōdhicaryāvatāra, 9.145
  • Muktāvalī, Pratyakṣa Khaṇḍa
  • Māthurī Ṭīkā on Tatvaciṃtāmaṇi
  • Nyāyakaṃdalī
  • Nyāyakaṃdalī Sādharmya Prakaraṇa
  • Nyāyasūtra, 1.1.4
  • Nyāyasūtra, 3.1.32
  • Nyāyasūtra, 3.1.43
  • Prasannapadā Ṭīkā on Nyāyasūtra, 3.1.43
  • Prasannapadā Ṭīkā, 3.1.49
  • Svōpajñabhāṣya on Abhidharmakōśa, 1.4.3
  • Tarkabhāṣā
  • Vēdāṃta Paribhāṣā
  • Yōgadarśana Vyāsabhāṣya, 1.7
  • Śāṃkarabhāṣya on Brahmasūtra


(Dwivedi, Satyam, and Munish Kumar Mishra. “Indian Wisdom on Ocular Perception and Cognition.” The Original Source, IV, no. 17, July 2017, pp. 89–94.)



Dr Munish Kumar Mishra
Guest faculty,
Department of Vaidic Darshan,
Banaras Hindu University

PC: Shivam Dwivedi

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