Our use of language often highlights a peculiar gap between perception and reality. We describe the sun as rising and setting, a notion embraced by both scientists and gardeners alike. Yet, the sun does not move in this manner; instead, it is the Earth's rotation that creates this visual experience. Philosopher Martin Lee Mueller notes that Nicolaus Copernicus' heliocentric model inflicted a 'fatal wound' on the Western psyche, illustrating that:

“Copernicus’s overturning of the geocentric model definitively proved that you could not trust your senses.”

For René Descartes (1596–1650), the realization that the geocentric view was incorrect—recognizing that the Earth orbits the sun—prompted him to pursue a philosophical foundation that could provide certainty in our understanding of the world.

Descartes pondered: if our perceptions of nature are mere illusions, then what can we rely on to know the true nature of reality?

When our senses perceive a luminous sphere traversing a stable Earth, and it turns out to be a misconception, it becomes clear that we need a new basis for knowledge. This foundation must differentiate our deceptive physical precepts from our intellectual concepts, as only the latter can truly grasp reality.

It was not solely the heliocentric theory that bewildered Descartes. Galileo had previously encouraged skepticism about our sensory experiences, asserting that mathematics was the only reliable guide through the 'dark labyrinth' of sensory perception. As Galileo articulated:

This grand book the universe … is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it; without these, one wanders about in a dark labyrinth.

This perspective led Descartes to doubt all knowledge obtained through the senses. The only certainty he could find was in his own self-aware, conscious thought, which he termed res cogitans: the intellect, the mind, and the soul. He posited that language, or logos, was the defining trait that distinguished humans from animals, which he deemed incapable of such complexity.

Descartes’ delineation of the human mind as unique from the soulless realm of nonhuman beings and the physical world created a profound divide that continues to echo in contemporary thought, often referred to as the 'Cartesian Split':

“With that Cartesian split,” Mueller observes, “a deep ontological crack began to shoot far and fast through the phenomenal world, not unlike when lake ice relieves its inert tension in a rumbling boom that reverberates through the frozen landscape, leaving behind a jagged lake surface.”

However, Descartes’ division did not merely disconnect the human mind and soul (res cogitans) from the mechanical aspects of nature (res extensa). It also invigorated the "Great Chain of Being," positioning humans at the pinnacle of life's hierarchical continuum.

For Descartes, humans were exceptional because of their blend of soulful thought (the mind) and mechanical existence (the body). This led him to a bleak conclusion: since only humans could reflect on their bodily sensations and the emotions they evoke, only they could experience pleasure or pain. Nonhuman animals, in his view, were akin to mindless machines—automatons devoid of thought or feeling.

The legacy of Descartes’ split is still evident today when discussions arise about whether animals experience emotions. The perception of animals as unthinking entities has historically justified widespread exploitation and experimentation. Some animal researchers, such as primatologist Frans de Waal, strive to mend the rift Descartes created, addressing the ingrained beliefs of human dominance over animals.

For numerous environmental historians, the Cartesian split serves as a critical starting point for addressing our current ecological crises. It signifies the emergence of a damaging dualism in modern society: a separation of mind from body, humans from animals, and society from nature. This dualism not only alienates humans from animals but also promotes the idea of human superiority over both animals and nature.

Moreover, as ecofeminist philosopher Val Plumwood explains, Descartes' assertion of human superiority over the nonhuman world—positioning human exceptionalism against the backdrop of an unthinking, mechanical nature—also entails a denial of our dependence on the natural world for our mutual well-being. She writes:

“What is involved in the backgrounding of nature is the denial of dependence on biospheric processes, and a view of humans as apart, outside of nature, which is treated as a limitless provider without needs of its own.”

Long before and since Descartes’ bifurcation of humans from animals, our understanding of humanity has been intricately tied to how we define what is not human and often less than human. This legacy has fostered a hierarchy of nonhuman beings that places us atop. It has perpetuated the notion of human evolution as a blend of biological advancement and progress, leading many—especially those who are white and male—to view humanity as the apex of evolution rather than a mere component within the web of life.

As writer Maria Popova notes, “even Darwin, who radicalized our understanding of nature by demonstrating the evolutionary ladder of life, scribbled in the margins of a natural history book: ‘Never say higher or lower. Say more complicated.’”

In his 1928 work The Outermost House: A Year of Life on the Great Beach of Cape Cod, nature writer Henry Beston challenges the enduring influence of Descartes on our perceptions of nonhuman animals. Observing a flock of birds, Beston poses:

“By what means, by what methods of communication does this will so suffuse the living constellation that its dozen or more tiny brains know it and obey it in such an instancy of time? Are we to believe that these birds, all of them, are machina, as Descartes long ago insisted, mere mechanisms of flesh and bone so exquisitely alike that each cogwheel brain, encountering the same environmental forces, synchronously lets slip the same mechanic ratchet? or is there some psychic relation between these creatures?”

This reflection reveals Beston’s desire to break the spell of Descartes’ human exceptionalism—a flawed belief in human superiority that quiets the nonhuman world and reduces the Earth to a mere stage for human narratives.

To counteract Descartes’ viewpoint, Beston’s writing serves as a form of magic that seeks to position ‘Nature in the Active Voice,’ as Val Plumwood articulates.

Or, as naturalist Sy Montgomery states, we require a language that helps us perceive that:

“Our world, and the worlds around and within it, is aflame with shades of brilliance we cannot fathom — and is far more vibrant, far more holy, than we could ever imagine.”

Ultimately, Beston concludes that to heal the fracture instigated by the Cartesian split, we must radically rethink what it means to be human in a world shared with other beings. We need to reject the illusion of separation from nature, resist any denial of our interdependence with nonhuman life that Descartes promoted, and remain open to the mystery of our ecological interconnectedness. In summary:

“We need another and a wiser and perhaps a more mystical concept of animals. Remote from universal nature and living by complicated artifice, man in civilization surveys the creature through the glass of his knowledge and sees thereby a feather magnified and the whole image in distortion. We patronize them for their incompleteness, for their tragic fate for having taken form so far below ourselves. And therein do we err. For the animal shall not be measured by man. In a world older and more complete than ours, they move finished and complete, gifted with the extension of the senses we have lost or never attained, living by voices we shall never hear. They are not brethren, they are not underlings: they are other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendour and travail of the earth. For the gifts of life are the earth’s, and they are given to all, and they are the songs of birds at daybreak, Orion and the Bear, and dawn seen over ocean from the beach.”

–Henry Beston, The Outermost House: A Year of Life On the Great Beach Of Cape Cod

description:	How two sentences in Leopold’s famous essay, ‘the land ethic,’ became so widely influential, and so widely misunderstood.