In the 13th-century, western Europe rediscovered Aristotle's books on natural philosophy, or natural science ('Libri naturales'), and this caused an intellectual revolution. Despite being banned in Paris early in the century, they quickly became part of the curricula of universities. Oxford, where this manuscript was probably made, was a leading centre for the study of Aristotle. All students had to read set texts of Aristotle's treatises with commentary, of which this book is an example. It is exceptional, though, because it is quite richly decorated with unusual images. Furthermore, it belonged to Nicholas of Cusa, a German theologian and cardinal, in the 15th century. The third book is called 'On Coming Into Being and Passing Away' ('De Generatione et Corruptione') and concerns chemical transformations and conditions of existence. In this manuscript, its first letter bears a picture showing a couple in bed and a nursemaid looking over an infant in a cradle nearby. Over the couple's bed, a window, its curtains billowing inward, is open to the night sky. This image may have been modelled upon one in a secular book or possibly another scientific book, since the heavens were believed to influence humans at their conception and birth. The actual text by Aristotle is in the centre of the page, in larger writing. Surrounding it are the commentaries, much needed by the student who was expected to study Aristotle's notoriously difficult writing. One medieval theologian had called him 'the sphinx'.