The Jesuits named the mission for Saints Cosmas and Damian, twin brothers of the third century who practiced medicine and, by tradition, took no payment for it. It was a fitting patronage for a place built on care and craft. San Cosme y Damián sits in the Itapúa Department about 80 km west of Encarnación, hard against the Paraná River where Paraguay meets Argentina, a district of some 800 square kilometers and around 10,000 people. The reduction grew from the same Jesuit effort that spread out from San Ignacio Guazú in the early seventeenth century, gathering Guaraní families into a community organized around faith, farming, and skilled work - the pattern repeated all along this stretch of river country.

Suárez was born in 1679 and arrived at the mission as a young man, where he turned a remote outpost into a working observatory. With the help of the Guaraní, he ground lenses and built telescopes, a pendulum clock, an astronomical dial, and a sundial - rudimentary by European standards, yet accurate enough to do real science. He used quartz drawn mostly from the Paraná and a tube he could raise on a wooden frame with harnesses and pulleys. From the church tower he recorded eclipses of the sun and moon, the satellites of Jupiter, and the rings of Saturn, then sent his notes back to Europe, where scientists hungry for observations from the southern sky took notice. This was not a hobbyist. It was the southern hemisphere joining the scientific conversation, from a mission on the edge of the map.

Suárez's masterwork was a book with an audacious title: Lunario de un Siglo, a "lunar almanac of a century." Published in the 1740s, it predicted, with remarkable accuracy, the eclipses that would fall between 1740 and 1841 - a full century of celestial events calculated by hand at a Paraguayan mission - and folded in geographical data for some seventy cities besides. Almost all of his instruments have since been lost. Only the sundial survives, still standing in the old schoolyard where the mission's children once learned. It is a small, weathered thing to carry such a large legacy, but it marks the spot precisely: here, a man and his Guaraní collaborators measured the heavens and got the answers right.

Most Jesuit missions in Paraguay are ruins you visit. San Cosme y Damián is different - it holds the only mission church in the country still in continuous use, a place of worship and a community center without interruption to this day. Inside are original wood carvings, some keeping their first coats of paint, and among them figures of Jesus rendered with indigenous features - the Guaraní artists shaping the sacred in their own image. The painted ceiling and the stone ornaments the inhabitants made are still there to see, as are the well-preserved school and priests' rooms; as recently as 2022 part of the mission remained unexcavated, its story not yet fully told. Today the district lives by farming, livestock, and fishing, and like many rural towns it watches its young people leave for Encarnación, Asunción, or across the border. But the church endures, and so does the memory of the priest who looked up.