As darkness settled over the small German town of Jena in the late winter of 1798, large groups of young men rushed to the town university’s biggest auditorium to listen to their new philosophy professor. They jostled for seats, took out ink and quills and waited. At the lectern, a young man lit two candles. He most likely couldn’t make out the students’ faces, but they saw him bathed in light.

There is a “secret bond connecting our mind with nature,” the professor, Friedrich Schelling, told the students. His idea, that the self and nature are in fact identical, was as simple as it was radical. He explained this by pointing to the moment when the self becomes aware of the world around it.

“At the first moment, when I am conscious of the external world, the consciousness of my self is there as well,” he said, “and vice versa — at my first moment of self-awareness, the real world rises up before me.” Instead of dividing the world into mind and matter, as many philosophers had done for centuries, the young professor told his students that everything was one. It was an idea that would change the way humans think about themselves and nature.

To me it seems that we sometimes forget that we’re part of nature — physically of course, but also emotionally and psychologically — and this insight is missing from our current climate debates. As a historian, I have looked at the relationship between humankind and nature, and I believe that Schelling’s philosophy of oneness might provide a foundation on which to anchor the fight for our climate and our survival.

Schelling was only 23 when he had become the youngest professor at the University of Jena that winter. He was part of a group of rebellious philosophers, poets and writers who lived and worked in the small university town about 130 miles southwest of Berlin. The circle included some of Germany’s most famous minds. There were the poets Goethe, Schiller and Novalis; the visionary philosophers Fichte, Schelling and Hegel; the young scientist Alexander von Humboldt, the contentious Schlegel brothers — Friedrich and August Wilhelm — as well as the latter’s wife, the free-spirited Caroline Schlegel (who would later divorce August Wilhelm and marry Schelling).

They worked, wrote, read and laughed together. They composed poems, drafted philosophical treatises and translated passages from great literary works. Most important, this “Jena set,” as I’ve called them, put the self at center stage and redefined our relationship with nature.

Unlike Isaac Newton, who had described matter as being essentially inert, or the French philosopher René Descartes, who had declared animals to be machines, Schelling’s so- called naturphilosophie (nature philosophy) questioned these mechanical models of nature. Instead, Schelling pronounced that everything — from insects to trees, stones to birds, rivers to humans — was part of one great organism.

For millenniums, thinkers had turned to their gods to understand their place and purpose in the unknowable divine plan. Then, in the late 17th century, a scientific revolution began to illuminate the world in a new way. Scientists peered through microscopes to see the minutiae of life and lifted telescopes up to the heavens to discover our place in the universe. They classified plants, animals and minerals into tidy categories to impose order on the natural world, and they dissected human organs and investigated blood circulation to comprehend how the body functioned. The ticktock of new and precise clocks became the rhythm of a productive society.

This new rational approach, though, also created a distance to nature — the external world had become something that was investigated from a so-called objective perspective. But no matter how much scientists observed and calculated, there seemed to be a more emotional and visceral connection between humankind and nature that could not be explained with scientific experiments or theories.

According to Schelling, being in nature — meandering through a forest or walking up a hill — was always also a self-discovery, a journey into oneself. It was a thrilling idea, and this philosophy of oneness became the heartbeat of Romanticism.

Contemporary travel accounts illustrate these changes. Many 18th-century travelers described a village, a city, a landscape or a country as detached observers — as individuals watching from a distance. They saw the countryside through the windows of their carriages and described art and architecture through the prism of their learning and books.

Then, in the early 19th century, as Schelling’s ideas spread, the young Romantics began to feel a deeper sense of connection to the world around them. Instead of just visiting museums and cities, this new generation scrambled into caves, slept in forests and hiked up mountains to be in nature. They wanted to feel rather than to observe what they were seeing. They wanted to discover themselves in nature.

Humboldt would later describe nature as an interconnected whole where everything was entangled in what he called “a wonderful web of organic life.” Humboldt had seen these connections during his five-year expedition through South America where he encountered many Indigenous peoples who had long regarded earth as alive and interconnected. Humboldt was also the first scientist to talk about environmental devastation caused by monoculture and deforestation during his exploration of South America.

Once nature is understood as a web, its vulnerability becomes obvious. If one part is damaged, other parts might suffer, too. This concept of nature still shapes our thinking today.

We live in a world of climate emergency — from rising sea levels and torrential floods to a striking loss of biodiversity and mass human migration. This summer there have been extreme and terrifying heat waves across Europe, Asia and the Americas and devastating floods in Pakistan but also in Yellowstone, Kentucky and St. Louis.

Today, the Jena set’s ideas of unity with nature have been imbued with a new and desperate urgency. For decades scientists and activists have tried to convince us with predictions and statistics — but somehow they don’t change our behavior. Most of us understand on an intellectual level what’s at stake, but that doesn’t seem to be sufficient.

There is a reason the iconic photograph of earthrise taken during the Apollo 8 mission in 1968 has become one of the most influential images in history and has been hailed as the beginning of the environmental movement. It was the first time that we saw our planet — like a small blue and white marble suspended in the vastness and blackness of space — in its wholeness and fragility. It’s the most potent visualization that we’re part of nature.

The Jena set explained this deep bond between humans and nature more than 200 years ago. We are nature, and Schelling’s philosophy of oneness reminds us that we’re part of a great thumping web of life. “As long as I myself am identical with nature,” Schelling insisted, “I understand what living nature is as well as I understand myself.” Just as the image of earthrise has inspired millions, so can Schelling’s philosophy of oneness.