 If the medieval tradition is being envisaged in all four of its main branches, there is some virtue in seeing the point of departure in the work of Plotinus (d. 270) and Porphyry (d. 305?) and including too the other Greek pagan material. All four branches are rooted in the so-called Platonic Schools, and they took their orientation from these two philosophers. Of course, historians of ancient philosophy will also want to include some of the thinkers in the earliest centuries of this period in their field, but that is not a problem, because there is no reason why periods in the history of philosophy should not overlap.