Some Research Methods Used by the Buddha as Recorded

Buddha taught the dhamma with the objective of bringing welfare and happiness to living beings. He admonished his disciples to wander for the welfare of the many, happiness of the many, and for the welfare of the gods and humans. As he stated, the objective of expounding dhamma is cessation of suffering or of unsatisfactory nature (not seeking anything in return or not seeking converts). The dhamma expounded by the Buddha can be examined by the wise and it is an open invitation to come and see (in Pali the characteristic is named as 'ehipassika').
When performing this compassionate service to the world Buddha, used various methods of teaching as well as techniques that help improvement of wisdom and liberation of the mind. Buddhist goal of liberation of mind can be attained by realizing the true nature of things (as impermanent, unsatisfactory and non-soul nature of the mind). All what we see are subject to change. Hence, we could treat the conditioned things as subjective. The Buddhist aim is to understand this subjectivity of everything. When this subjectivity is realized through understanding, the objective liberation of the mind becomes more realistic.
Buddha's teachings were not always conveyed verbally since it is a personal realization. His techniques included verbal techniques as well as other methods that improve understanding of a person. Three of these methods can be illustrated by citing happenings of the past.
Sampling and generalizations
Kisagotami was a member of a rich family in India. Her life was full of comforts before her marriage that she did not know the burdens of lay life. After her marriage she bore a child. As the child was growing up from its infancy a disease overpowered the baby and he died. Sorrow overpowered Kisagotami's mind. Due to this sorrow she was unable to accept the death of her child. Losing the touch of reality due to the sorrow she thought the child had just fallen ill and it was possible to find a cure for this illness. She started wondering around in the city of Savath with the dead baby in her hands looking for medicine to cure her child. She asked for some medicine from everyone she met. Ultimately, some kind folks in the city directed her to the Buddha. They said, "there is the Buddha in Jeta's grove, he'll be able to cure your baby." She followed their advice and went to the Jeta's grove. There the Buddha was teaching and discussing dhamma with the seekers at that time. Kisagotami hurried towards the Buddha and placed the dead body of the baby in front of him. She pleaded to the Buddha, "please sir, cure my baby and help me." Buddha understood the mental state of Kisagotami. He did not start preaching dhamma or attempted to show his miracle powers. Instead he asked Kisagotami to bring a handful of mustard seeds. These mustard seeds should be from a household where no one had died before.
Kisagotami started her search. Still carrying a dead body she went from house to house. She asked for mustard seeds from the first house. The occupants of the house gladly gave the seeds. Then she asked the important question, "had anyone died in the household?" The answer to this question was the list of the people that had passed away (grandparents, other elderly etc.). She went to the second house, third house etc. The search continued. From all the houses she could find the mustard seeds but in each one of them someone had died. Finally, she realized that death is part of the nature of life. With this realization she gained her mental senses. She realized what had happened to her beloved baby. She placed the baby in a cemetery and hurried to meet the Buddha. After joining the bhikkuni order (the women disciples of the Buddha), she practiced according to the Buddha's instructions and attained the final liberation of the mind.
In this case, the Buddha's hypothesis is that death is natural and it overcomes everyone when the conditions are there. His survey method made Kisagotami realize the truthfulness of this hypothesis. This was more than just a statistical proof. This realization was strong enough for her to come to proper senses and realize the true nature of everything. The null hypothesis would have been immortality (in which Kisagotami was attempting to believe). There was no evidence of this. In her search she went to enough households until she realized (until the sample was adequate for the realization). From her observations, she was able to generalize and understand the nature of life and attain inner or mental peace and happiness to realize the sorrow free state of Nibbana.
Experimental Observations
At some other occasions, Buddha created controlled environments to understand the truth. Again we can look at the case of a monk who was given instructions to perform an experiment. In this case, the monk's name was Chullapanthaka. Let us call him Panthaka. He ordained under his brother and was attempting to learn teachings of the Buddha. However, he was unable to memorize even a four-line stanza. His brother asked Panthaka to leave the Bhikkhu order. Buddha came to know about this and out of compassion for Panthaka instructed him to perform a very simple experiment rather than attempting to memorize a stanza. Early in the morning Buddha gave Panthaka a clean piece of white cloth. Asked him to sit in one place facing the east direction and to rub the piece of cloth with both hands. While rubbing this cloth, he was asked to repeatedly utter the statement- "removing dirt." This was a very simple and easy task for Panthaka compared to leaving the order or memorizing the stanza. He was so absorbed in the activity. As the time passed by the sun moved from east to west. Gradually the white piece of cloth became dirtier also due to his rubbing of it. He realized the changing nature of things and the necessity to remove the defilement of his mind. He understood the true nature of the conditioned things. The white cloth changed its color. Sun started setting. The conditions for purity changed and the cloth changed its color. The conditions for the sun to stay in the east changed and it was in western direction. Similarly the other conditioned things change too as the conditions change. Panthaka liberated his mind from the impurities. He was able to attain inner peace, tranquility and liberating wisdom.
In this case Buddha's method was experimentation in modern terms. He created a more controlled environment for Panthaka to make his observations. Panthaka succeeded in this experiment and gained.
Case Research
In modern days we use case research in social sciences. Buddha's application of this method can be seen when we study various Jataka stories. Sometimes, we have the misconception that they are good only for small children. However, when we understand the context and the purpose of the story we can understand that the Buddha was relating a tale as a case study (from the modern day sense). When hearing this story the listeners were able to understand the situation they were in. They were able to connect their present situation to the past happenings in the story. As a result the listeners were able to understand the truth. They were able to understand the nature of the life, nature of the world or the four noble truths proper.
Even today we can understand many phenomena in human nature as well as in society by reading them. It is necessary to pay attention to the purpose of them as well as to the context as conveyed in the stories (rather than getting immersed in literary details in them).
The above three methods provide some insights about the openness in Buddha's teaching and his emphasis on investigations leading to improved understanding.
Isn't impartial observation and reflection important in daily life?