There are moments in history when the terminology, the categories, and the tools we use to make sense of the world reach a state of obsolescence. I believe we are experiencing such a moment. Our way of thinking, built around walls, doors and other architectural metaphors, crystallized somewhere in the 17th–18th century at the time when human ambitions to comprehend and systematize the world blossomed. It is perhaps best illustrated by the controversy that opposed two major figures in the field of natural history, the Swedish physician and biologist Carl Linnaeus and the French intendant of the king’s garden, Georges- Louis Leclerc de Buffon. At the time, the dominant question was: How can the world be comprehended, organized and formalized? Linnaeus won this intellectual dispute: the world was to be known through classification and taxonomy, creating strictly discrete categories and hierarchies. Buffon had argued in favor of a more nuanced vision of the living world. He had advocated a patient observation of nature, an attention to varieties and variations, and a sensitivity to what could not be neatly attributed to specific species. To little avail. The notion of walls we are discussing at the present conference, if we understand walls both as physicality and as metaphors, is largely heir to Linnaeus’ worldview.