Aptopadesha in Hinduism are the words of a trustworthy person. Gautama, the founder of the Nyaya School of philosophy, defines sabda (verbal testimony), a source of valid knowledge, as apthopadesha (aptopadesha sabdah – Nyaya Sutra 1.17)
Upadesha means verbal instruction or communication. The knowledge of an object through such verbal communication is verbal knowledge. It is this aspect of verbal communication that distinguishes sabda as a pramana (means of valid knowledge) from other pramanas.
All verbal knowledge, however, is not valid. For instance, the deceptive sentences of a scoundrel are not valid. To differentiate valid verbal knowledge from a non-valid one, the adjective apta is added to upadesha in defining shabda as a pramana in Nyayasutras.
An Apta is a person who is trustworthy. Vatsyayana while commenting on Nyaya Sutras, defines apta as one who:
- Possesses direct and valid knowledge
- Intends to communicate his knowledge correctly
- Has the ability to communicate his knowledge adequately
A person who is devoid of any of the above characteristics cannot be regarded as apta.
Vatsyayana clarifies further that the term apta is not restricted to a learned person.
This suggests that anyone who has knowledge and is able to communicate effectively with a desire to help others would be an apta irrespective of his social status.
The status of being an apta is equally applicable to a sage, an arya or a non-arya.
According to Nyaya, the term apta is not restricted to human assertions alone. Nyaya admits two kinds of Shabda: Vaidikashabda (scriptural) and laukika shabda (empirical).
Vaidikashabda is perfect and infallible by its very nature as it is the word of God, who is an apta, while laukikasabda is what is expressed by trustworthy person.
Source – Nyaya Sutra of Gautama by Ganganath Jha published in 1939 by Poona Oriental Series
Nyaya Kusumanjali of Udayana, 1968, written by Udayan Acharya – published by Bharatiya Vidya Prakashan.
Encyclopedia of Hinduism - Volume 1 - page 345