As with physical goods, sustainability of knowledge requires not compromising future generations’ ability to enjoy the right to use it—while still giving overriding priority to ensuring access to that right for the world’s poor. Unlike physical goods, however, knowledge has a unique capacity not to be diminished through use, a quality often expressed in the image of one candle lighting another. This chapter examines what the sustainability of the right to knowledge—and the right to sustainable knowledge—means both practically and conceptually. Knowledge is not only an abstract concept, but requires work to produce, update, and maintain. While incremental, intergenerational progress may seem the only realistic path for achieving this sustainability, the affordances already outlined in this book suggest the possibility of transformative changes to institutions, knowledge, and practice that could open up as-yet-unimaginable pathways toward that future.