It is said that Siddhartha's critical awareness began at age twelve when he participated in a farming festival. Following his father outside the palace for the first time, he was shocked by the scenes of ordinary life he encountered. Farmers were plowing the fields, but they appeared extremely emaciated, covered in dirt, wearing torn clothes, and their faces were distorted with suffering. They were nothing like the people Siddhartha had seen in the palace. Saddened, Siddhartha asked the farmers, “Why are you living in such suffering?” It was then that he vaguely realized that the comfort and abundance he had enjoyed were not simply given but built upon the suffering of others.

Siddhartha decided to renounce the world. However, knowing it would be impossible to gain his parents’ permission, he secretly left home at night and began the life of an ascetic. Having finally become a practitioner, which he had wanted to for over 10 years, he thought he would soon attain enlightenment. He endured the harsh sounds of wild animals, was bitten by insects, and suffered through hunger and cold. Memories of warm beds and nourishing food crept into his mind. As time passed, he was increasingly consumed by doubt and regret. When Siddhartha recognized his own feelings of remorse, he rebuked himself. Reflecting on his inadequacies and foolishness, Siddhartha decided it would be difficult to practice alone and set out to find a teacher.

Siddhartha entered Dungeshwari, a forest near Gaya where corpses were abandoned, and devoted himself to six years of extreme asceticism. Despite his intense practice, he was unable to attain enlightenment. At that point, Siddhartha reflected deeply on his life. In his youth before renouncing the world, he had simply followed his desires. Although satisfying those desires brought joy and pleasure, the path of hedonism did not lead to true liberation from suffering. After renouncing the world, he then swung to the opposite extreme, walking the path of asceticism, denying and suppressing all desires. However, Siddhartha realized that both indulging in desires and suppressing them were extremes and not the true path to liberation. It was then that he discovered a third way of letting go of both extremes. This is called the "Middle Way."

Having discovered a new path and a new perspective, the Buddha sat beneath a Bodhi tree in a lush forest across the river, on a seat of Kusha grass given by a shepherd boy, and practiced diligently. The Buddha no longer practiced with rigid determination, firm resolution, and tension. Instead, he practiced with ease, maintaining a clear awareness. Under the Bodhi tree, he entered deep meditation in a state of peace. In the stillness of the early morning, when the morning star appeared in the sky, he finally attained enlightenment. It was as if a light had been turned on in the darkness, revealing the true nature of the world. Until then, the world had seemed like a collection of countless independent entities, competing with one another for survival. But when the Buddha attained enlightenment, he saw that the true nature of the world was not like that. All beings are not separate and independent; they are all interconnected. This is known as “dependent origination.”

Upon realizing the Law of Dependent Origination and seeing the true nature of reality, all the questions the Buddha had as a child were resolved. In the Indian caste system, it was believed that Brahmins and royalty were inherently separate from commoners and slaves. However, the Buddha saw that all beings were interconnected. Similarly, in any society, nobles and commoners are not inherently distinct; they exist in relation to one another. If commoners disappear, nobles also disappear; if nobles vanish, so do commoners.

Thus, the Buddha taught that notions of superiority and inferiority are not intrinsic to beings themselves but are merely errors in human perception. At the time, this realization was profoundly revolutionary. He expressed it this way: "This exists because that exists; this ceases because that ceases. This arises because that arises; this perishes because that perishes."

Venerable Ananda, who attended to the Buddha, once approached him and asked, "Can a woman not attain enlightenment if she renounces the world and practices diligently?" The Buddha answered that women, too, could achieve enlightenment through dedicated practice. Ananda then asked again, "Then why do you not allow women to renounce the world and join the monastic order?" Persistently, Ananda continued, "Please allow women to enter the monastic community under your precepts and teachings." The Buddha eventually said, "I allow the ordination of women." Thus, women's ordination was permitted.

The Buddha’s decision to allow women to join the monastic community was truly groundbreaking for the time. Even today, in the 21st century, Catholic nuns cannot be ordained as priests. In India, gender discrimination remains even more severe than caste discrimination. Allowing women to be ordained 2,600 years ago in such a society was far more revolutionary than we might imagine. The ordination of women can be seen as the beginning of women's liberation and gender equality. In particular, the fact that women could have their own names, independent of being someone’s daughter, wife, or mother, was a remarkable achievement. Through ordination as bhikkhunis, women were able to claim their own identity for the first time. The Buddha was truly a pioneer of women’s liberation.

The Buddha did not discriminate against the untouchable outcastes, who were believed to be impure and capable of tainting others through physical contact. Instead, he taught them the Dharma and guided them with compassion. One of the most well-known examples is the story of Nidai, a man who carried human waste. One day, the human waste Nidai was carrying splashed not only on his own clothes but also on the Buddha’s robes. Horrified, Nidai fell to his knees and begged for forgiveness, believing he had committed an unforgivable offense. However, the Buddha gently took his hand, helped him up, and led him to a river. After washing their clothes together, the Buddha asked, “What happened after washing the clothes?” Nidai answered, “They became clean.” The Buddha then said, “Exactly. This cloth was not inherently dirty. It became dirty because something unclean stained it, but once washed, it became clean again. In the same way, no person is born impure. People only become tainted by impurities. Just as we wash dirt off cloth, you can cleanse impurities from your heart.”

A young man was struggling with his practice. He went to the Buddha and asked, "The Brahmins say that no matter how many sins a person commits, if they bathe in the Ganges River, all their sins will be washed away, and they will be reborn in heaven. Is that true?" Hearing this, the Buddha smiled and said, "If what the Brahmins say was true, then the fish living in the Ganges would be the first to be reborn in heaven."

Ananda asked the Buddha, "We have gained great merit by offering alms to you, but where should we make offerings to gain great merit after you enter nirvana?" The Buddha replied, "Ananda, do not worry. There are four ways in this world to gain the same merit as making offerings to the Buddha. First, offer food to the hungry. Second, give medicine to those who are ill and help them heal. Third, support and comfort the poor and the lonely. Fourth, protect and support those who practice with purity."

Up to this point, we have reexamined the life of the human Buddha from a modern perspective?a person who lived as a practitioner, an enlightened one who showed compassion to the marginalized, and a revolutionary who transcended his era. By reflecting on the life of Siddhartha who lived as a man within the society of ancient India, we come to realize that the Buddha was a true revolutionary. He was not a revolutionary who changed the world through physical force, but a great spiritual revolutionary who awakened people from ignorance and opened the door to a new world.

I hope that those of you reading this book will come to view the "revolutionary Buddha" I have discovered as a guide toward overcoming the era of climate crisis.