This volume belongs to the first new critical edition of the works of Francis Bacon (1561-1626) to have been produced since the nineteenth century. The edition presents the works in broadly chronological order and according to the best principles of modern textual scholarship. The seven works in the present volume belong to the final completed stages (Parts III-V) of Bacon's hugely ambitious six-part sequence of philosophical works, collectively entitled Instauratio magna (1620-6). All are presented in the original Latin with new facing-page translations. Three of the seven texts (substantial works in two cases, and all sharing a startlingly improbable textual history) are published and translated here for the first time: these are an early version of the Historia densi, the 'lost' Abecedarium, and the Historia de animato & inanimato. Another - the Prodromi sive anticipationes philosophiae secundae - has likewise never been translated before. Together with their commentaries and the introduction they open the way to important new understandings of Bacon's mature philosophical thought.