Mr. Wahid, affectionately known by his nickname Gus Dur, died Wednesday in Jakarta at the age of 69. A descendant of Javanese kings, he studied religious affairs in Egypt and Iraq before returning to Indonesia, where he worked as a journalist and academic. He was a three-term chairman of the Nahdlatul Ulama, a 40-million strong Muslim organization founded by his paternal grandfather, where he championed liberal ideas of religious tolerance, democracy and freedom.

Indonesia's chance to realize these ideals came suddenly in 1998, with the fall of Suharto. Mr. Wahid threw his hat into the presidential race the following year to "be the voice of clean politics." He won after Islamic parties threw their votes behind him. Markets fell, worried that the almost-blind cleric didn't have what it took to lead a vast archipelago struggling to cement its young democracy, and fracturing at its edges.

But Mr. Wahid proved them wrong. In only two years, he asserted civilian control over the military, revoked anti-Chinese legislation and encouraged press freedom. Most importantly, he condemned religious violence, argued strongly for a secular state and reached out to democracies around the world—including Israel.

Though he was eventually impeached by the legislature in a political putsch, Mr. Wahid proved just as courageous out of high office as he was in it. He lent his name and prestige to the Wahid Institute and the LibForAll Foundation to spread his vision of a modern, progressive and tolerant Islam both within Indonesia and around the world. After 9/11 and the Bali bombings, he spoke out strongly and often against terrorism.

Many Muslim Indonesians considered Mr. Wahid a living saint. But Christians, Buddhists and many others mourned his passing last week. Their grief is testament to the power of his ideas, not just for Indonesians, but for every other pluralistic society seeking a peaceful and prosperous future.