Carbon is not the enemy, says architect and sustainability leader William McDonough, the author and inventor of the concept of “cradle-to-cradle”. In the climate conversation, almost all references to carbon are negative. We talk about needing to aim for “low carbon,” and “zero carbon”. But McDonough thinks that it’s framing the problem (and solutions) in the wrong way. Humans are made of carbon. The plants and animals we eat are made of carbon. Carbon in soil is the basis of healthy ecosystems. When carbon is locked up inside diamonds or recycled in plastic, it’s a useful tool, not a pollutant. McDonough argues for new phrases. “Living carbon” is growing in biological cycles. “Durable carbon” is locked inside stable solids, like the wood inside a building or the paper in a book. Only “fugitive carbon”—carbon that has ended up somewhere unwanted, like carbon dioxide released into the atmosphere—is a problem.