It is a curious fact that many of the sources for the Presocratic and Stoic philosophers are early Christian authors; similarly, one can even find an echo of Parmenides in a Gnostic treatise from Nag Hammadi. Such writers were often dependent for their knowledge on a whole chain of previous interpretations and traditions, and it is these with which Professor Mansfeld is here largely concerned. He has tried to discover what in an earlier writer - Plato, and Aristotle, of course, as well as the Early Greeks - was of interest to a later one, notably the Middle Platonists. These articles demonstrate the value of such an approach, showing how a familiarity with the later history of an idea, say in a Gnostic text, can contribute to the understanding of the idea itself; or how the study of the selection of ideas used by Philo, for instance, not only sheds light on his own projects, but also helps explain why some motifs survived and not others, and why philosophical thought took the directions it did.
