The Vatican codex, which contains the complete text of Spinoza's "Ethics," is the only surviving manuscript of this work and constitutes a document of great importance. On 23 September 1677, it was handed over to the Roman Holy Office by Spinoza 's former friend Niels Stensen who had converted to Catholicism in 1667. Thus, it predates the publication of the "Opera Posthuma," which is dated 1677, but which did not in fact appear until the first months of 1678. Recent research and fresh documentation allow us to determine the several stages of the manuscript 's life before it reached Rome, where it was kept in the Archive of the Holy Office, and subsequently, transferred to the Vatican Apostolic Library, in 1922. Leen Spruit and Pina Totaro discovered the original manuscript here.