Bessarion was an avid collector of books during his entire lifetime. After he became a cardinal and had considerable financial means at his disposal, he managed to assemble one of the largest private collections of Greek and Latin manuscripts of his time. Shortly before his death, he donated his entire library to the Republic of Venice and made it a condition of this bequest that his collection should be kept in one place and not sold or otherwise dispersed, that it remain accessible to all who wish to consult it and that a library be built to house what he rightly considered a veritable treasure. His donation laid the foundations of the Marciana Library. One of his most prominent achievements was a philosophical treatise entitled In Calumniatorem Platonis, which is now recognised as both the last philosophical work of Byzantine civilisation and the first major philosophical treatise to appear before the writings of Marsilio Ficino and Giovanni Pico della Mirandola.