The Paul Hertz collection consists of correspondence, biographical material, manuscripts, offprints, and books from his library. Hertz's correspondence numbers over 100 letters, and many are with prominent individuals like Max Abraham, Albert Einstein, Max Planck, H. A. Lorentz, and Moritz Schlick. Biographical material testifies to the significance of Hertz's scientific achievements, their belated acknowledgment, and the intellectual milieu of his time. Included are an essay on Paul Hertz by his son Rudolf Hertz, a transcript of an oral history interview with Rudolf Hertz, and excerpts of published material relating to Paul Hertz's life and work. An extensive collection of offprints illustrates his interest in the work of others; annotations and dedications on some items reflect with whom Hertz exchanged ideas. The manuscript material comprises numerous, mostly unpublished writings from different stages of Hertz's intellectual development. Present are essays, notes, and drafts of papers, the titles of which range from "Vom Wesen der Logik" and "Uber Identitat" to "Kritische Bemerkungen zu Reichenbachs Behandlung des Humeschen Problems." There are also many untitled, incomplete writings in the collection and some handwritten pieces by Paul Ehrenfest that are likely unpublished. About 30 books from Hertz's library are present, some of them lightly annotated, including his own publications and others.