One of the most inventive artists of the twentieth century, Hilma af Klint was a pioneer of abstraction. Her first forays into her imaginative non-objective painting long preceded the work of Kandinsky and Mondrian and radically mined the fields of science and religion. Deeply interested in spiritualism and philosophy, af Klint developed an iconography that explores esoteric concepts in metaphysics, as demonstrated in Tree of Knowledge. This rarely seen series of watercolors renders orbital, enigmatic forms, visual allegories of unification and separateness, darkness and light, beginning and end, life and death, and spirit and matter. Published on the occasion of the exhibition Hilma af Klint: Tree of Knowledge at David Zwirner New York in 2021 and David Zwirner London in 2022, this catalogue features a text by the art historian Susan Aberth examining af Klint's spiritual and anthroposophical influences. With a conversation between the curator Helen Molesworth and the US Poet Laureate Joy Harjo discussing connections between Tree of Knowledge and native theories about plant knowledge, the publication broadens the scope of philosophical interpretations of af Klint's timeless work. Also included is a newly commissioned essay by the celebrated af Klint scholar Julia Voss, a contribution by the artist Suzan Frecon, and a text by art historian Max Rosenberg that further develops the conversation around why af Klint's work was not recognized in its time.