Among the most creative and influential scholars of the past 50 years, the protean Bruno Latour was variously described as a sociologist, a philosopher, and an anthropologist. But just as his work questioned the making of categories, he himself transcended categorization. For decades, Latour worked at the Center for the Sociology of Innovation (CSI) at the Paris School of Mines. In 2007 he became a dean at the prestigious Paris Institute of Political Sciences (Sciences Po), where he elevated the role of research by establishing its Médialab, a unique experimental space for transdisciplinary work, and integrated environmental concerns—especially climate change—throughout the Sciences Po curriculum.

Latour was a founding figure of our field, science and technology studies (STS). Beginning with Laboratory Life (1979, with Steve Woolgar), Latour asked the really big questions. What exactly is science? How do scientists, together with their equipment, facilities, and institutions, generate facts—and what are facts? Latour proposed that science in practice is an “agonistic field,” a scene of conflict and struggle. Pedestrian versions of STS explored the social context of scientific work. Latour, instead, challenged the very idea of a context separable from science itself. Latour’s studies of 19th-century French microbiologist Louis Pasteur subverted heroic narratives, arguing that Pasteur did not simply “discover” disease-causing microbes, effective vaccinations, and sterilization techniques; rather, he succeeded by enrolling a huge array of actors, including farmers and the anthrax bacillus itself. Pasteur brought “society” into the laboratory while taking the laboratory to the farm, the clinic, and the street.

Science in Action (1987) took this perspective further, famously presenting science as Janus-faced. One face, ready-made science, appears in textbooks as authoritative facts shorn of all authorship and disagreement, except perhaps the name of some individual “discoverer.” The other face, science in the making, is contentious, controversial, full of interpersonal and baldly political strife as scientists vie for funding, recognition, authority, and career-enhancing alliances with other actors both within and outside science. Latour’s key message: Follow the actors, and focus on controversy, because that’s where science is most… well, in action.

This way of thinking led to “actor-network theory” (ANT), an approach taken up well beyond STS. Actors, for Latour, could be both human and nonhuman; “acting” in the world did not require intentionality. “Actants” might be scientific instruments or microbes. They could be almost anything that affects outcomes, such as speed bumps that slow traffic. Actors seek to enroll others in their projects, building networks that accrue momentum. They seek to end debates—over speed limits, say—by delegating decisions to devices and other constructions. Alliances frequently shift and change, sometimes by deliberate action, sometimes by the nonintentional “action” of actants. To establish permanent footholds in the world, actor-networks establish “obligatory passage points,” such as genetic sequencing or climate models, through which other actors, such as public health officials or climate policy-makers, must travel.

In many ways, Latour was anti-theoretical. Pronouncing himself puzzled at the academic success of ANT, in 1999 he wrote that there were four things wrong with actor-network theory: the actor, the network, the theory, and the hyphen. In part he was stating the obvious: tracing actor-networks is less theory than method, one that involves tracking passage points, existing alliances, and changes of allegiance over time. ANT explains what happened by way of what happened; it explicitly claims that neither success nor failure, nor network scale, can be predicted in advance. Ever the provocateur, Latour was also seeking new ways of rattling the sociologists’ cage. In Reassembling the Social (2005), he insisted that “the social” itself acquired reality only through deployment in networks.

Latour deepened his experimentation with narrative forms in the 1990s. The strange but exhilarating Aramis (1992) traced the course of a failed 17-year project for a personal rapid transit system—one that resonates eerily with today’s self-driving vehicles. The book presents the traditional Author as one voice among many; others include project managers, politicians, and engineers, real archival documents, and fictional characters including a sociology professor, his student, and the unrealized Aramis system itself. As the various characters seek to explain Aramis’s fate, their every attempt to “apply” a social “theory” ends in confusion. The lesson lurks in the inherently contradictory, confusing, and unfinished quality of the facts themselves.

Latour constantly disputed the terms of modernity. In 1990, he famously claimed that We Have Never Been Modern; over two decades later, his mammoth anthropology of “the moderns,” An Inquiry Into Modes of Existence (2013) asked: “[I]f ‘we’ have never been modern, then what have ‘we’ been?” In his last two decades, he turned his full attention to the planetary crisis. His difficult Facing Gaia (2017) described a New Climate Regime in which “the Earthbound”—comprising scientists and all others who speak from, with, and for Gaia, Earth herself—must struggle with the “Humans” (perhaps, the moderns?) whose deities are markets and sovereign nations.

Latour loved theater, from impromptu skits at academic conferences to full-on theatrical productions, including a play, Cosmocolosse, and the Gaïa Global Circus. When his own scripts proved overly didactic, he engaged theater professionals to develop and stage them. He curated multiple exhibits of art and artifacts at museums around the world. In fact, Latour had planned to be in New York on October 27-28 for the North American Premiere of his performance piece with longtime collaborator Frédérique Aït-Touati, The Terrestrial Trilogy. It will now go forward without him. The list of his numerous collaborators would fill many pages. Among his many honors, those he valued most include the Bernal Prize of the Society for Social Studies of Science (1992), the Gifford Lectureship on Natural Theology (2013), the Holberg International Memorial Prize (2013), and the Kyoto Prize in Arts and Philosophy (2021), whose monetary award he donated to Sciences Po.

Ultimately, Latour took nothing for granted: not science, not society, not even “reality” or “existence.” Well, almost nothing. Earth, Gaia, is the ultimate obligatory passage point, the sine qua non of any mode of existence for humanity. Our planet will be a poorer place without him.