The philosophers of the Upanishads utilized various methods in their discussions and teachings!
The main methods followed by them were as follows:
1. Enigmatic method:
The best illustration of the egnimatic method is found in the Sevetasvatara Upanishad, where it is said that, Reality is like a great circumscribing felly whose tyres are the three Gunas, whose ends are the sixteen Kalas, whose spokes are the fifty Bhavas or conditions of Samkhya philosophy, whose couner-Spokes are the ten senses and their ten objects, whose six sets of eights are such as the eight Dhatus.
The eightfold prakriti and so on, whose, single rope is the Cosmic person, whose three paths are the Good, the Bad and the Indifferent or yet the Moral, the Immoral and the Amoral, and finally, which causes the single infatuation of the ignorance of self on account of the two causes, namely, good and bad works. Puzzles can also be found in the Isavasyopanishad and the other Upanishads.
2. Aphoristic Method:
Aphoristic method of the Upanishads has been widely used in the later philosophical treatises as well. In this method, knowledge is compressed in small aphoristic sentences, which require sufficient intelligence to understand them. It is for this reason that the same sentences have been interpreted differently by different commentators.
In the Mandukya Upanishad, it has been said, The syllable, ‘Om’ is verily all that exists. Under it, is included all the past, the present and future, as well as that which transcends time. Verily, all this is Brahman. The Atman is Brahman. This Atman is four-footed. The first foot is the Vaiswane, who enjoys gross things in the state of wakefulness.
The second is the Taijasa, who enjoys exquisite things in the state of dream. The third is the prajna, who enjoys bliss in the state of deep sleep and the fourth is the Atman who is alone, without a second, calm, holy and tranquil.” This passage has been differently interpreted in the different systems of the Vedantic philosophy.
3. Etymological Method:
In the etymological method, the meaning of word is explained according to its root. In the Brhadaranyaka Upanishad, we are told that “Purusa” is really “Purisaya” i.e., inhabiting the citadel of heart. Examples like this can be seen in other Upanishads, also.
4. Mythical Method:
Mythical method has been mostly used in teaching. In the Upanishad, e.g., in the Kena Upanishad, the parable of Indra and the demons has been told to preach the lesson of humility. Sometimes a myth is introduced for aetiological purposes, as, for example, the myth of the sun coming out of the huge world egg.
Sometimes one finds a transcendental myth. In the Aitereya Upanishad, e.g., it is explained how the Atman entered the human skull and became individualized as the human soul. Similarly, a myth is sometimes introduced for the sake of parody.
5. Analogical Method:
Things which cannot be explained by reasoning are explained by analogy. For example, Yajnavalkya introduces the analogy of the drum or the conch in order to explain the processes of the apprehension of the self. Aruni explains the non-difference of the individual soul from the universal soul by the analogy of the juices in constitution honey or the rivers in flowing into the ocean and being merged with it.
6. Dialectical Method:
The dialectical method is one of the most widely used methods of the Upanishads. In this method, the philosophers assembled at some place and dramatically discusses different problems among themselves. In the Upanishads such discussions and symposia have been mentioned at many places.
7. Synthetic Method:
In the synthetic method, the discussion of the dialectical method is replaced by the creative synthesis of the synthetic method. In the fourth chapter of the Brhadaranyaka Upanishad, Yajnavalkya synthesizes the several standpoints explained by king Janak. Example like this can be found in Chandogya, Prasna and other Upanishads.
8. Monologic Method:
Though the philosophers of the Upanishads speak very seldom in their own persons, yet when they do speak, they forget the presence of others and go on talking to themselves for a long time. In the Brhadaranyaka Upanishad, Yajnavalkya, replying to the question of king Janak, regarding the nature of the soul, is lost in self-speech. In the Kathopanisad, in the discussion of Yama and Nachiketa, Yama goes on talking to himself for a long time while replying to the third question of Nachiketa.
9. Ad hoc or Temporizing Method:
The teachers of the Upanishads taught their disciples according to their mental and psychological level. In the temporizing method, as the spiritual level of the enquirer rises, the teacher not only shows him the path ahead, but also tells him the whole truth gradually.
This method has been accepted as very important by the modern educational psychology. In the famous parable of Indra and Virochana, Virochana is satisfied by the first answer of his teacher Prajapati, but Indra is not satisfied and goes on questioning him.
Prajapati tells him the secret of the soul, first in the body, then in the dream and sleeping stages and it is after that alone that he explains to him the real nature of the soul. In this method, the enquirer himself struggles to understand the truth and the teacher only guides him. Hence, this method is very important for spiritual evolution.
10. Regressive Method:
The regressive method is in the form of many successive questions in which every new question carries us at the back of the answer to the previous one. Thus when Janak asked Yajnavalkya about the light of man, Yajnavalkya answered that it was the sun.
Janak kept on going to the back of answer after answer, carrying Yajnavalkya from the sun to the moon, from the moon to the fire, and from the fire to the Atman which exists behind them all as the light m itself. In the same Upanishad the regressive method had been used in the discussion between Yajnavalkya and Gargi.