Ole Skovsmose (2023) opens this, his magnum opus, with the image of walking around a city. He provides a moving (sic) story of his early visit to São Paulo thirty years ago, and the colourful varieties of street life he saw and experienced. He fell in love with the city (and with his wife Miriam) and chose to settle and make his life there. He likens critical mathematics education to a city which can be traversed by many routes from different starting points and directions. The power of this simile is that it is organic and growing, not a systematic and rationally planned production. Ole Skovsmose not only applies this model to critical mathematics education but also to mathematics itself. Mathematics is defined by its practices, not some rational reconstruction or map.