At some point in or shortly after 1607, the opening passage of Francis Bacon's earliest surviving philosophical work, Valerius Terminus of the interpretation of nature – the first version of what ultimately became Bacon's Instauratio magna – was copied into the natural philosophical notebook of Edmund Leigh (c. 1585–1658), a Bachelor of Arts at Brasenose College, Oxford. Whereas contemporary scribal copies of Bacon's political, religious, and legal writings are common, copies of his unpublished philosophical writings are rare, and tend only to be found in unique exemplars with a direct Baconian association. As such, the Valerius Terminus has hitherto only been known from a single manuscript, with corrections in Bacon's hand, that was first printed in 1734. The discovery of a ‘user’ copy in a student notebook is therefore significant for what it suggests about the circulation of Bacon's earliest philosophical ideas. This significance is enhanced by the fact that the new copy appears to record an early draft of Bacon's work.