The ten years which followed Leibniz's return from Paris witnessed the clash between dreams and reality which was to characterise many aspects of his adult life. Upon his arrival in Hanover, he soon realised that what was expected from him primarily, albeit certainly not exclusively, was to act as keeper of a provincial private library. After his appointment to the supreme court of appeal (Oberappellationsgericht) in Mainz at a very young age, his experience of working on juridical reforms of the first importance, his recent years interacting with leading intellectuals in Paris and London, and his outstanding results in fields such as mathematics and technology, Leibniz quite rightly did not feel that his new position was commensurate with his credentials. Notwithstanding his energetic and innovative work for the library, he always resisted being identified as the court librarian. In his mind, he had been appointed as a court counsellor who, among other things, saw to the improvement and rationalisation of the ducal library collections; but who had projects infinitely grander for consideration by the duke. Despite the struggle to clarify his status and to be promoted, Leibniz found in Duke Johann Friedrich a supportive patron who gave a sympathetic hearing to his encyclopaedic plans for the reform and development of the sciences aimed at the defence and advancement of the Christian religion and at the promotion of the ‘common good’.