It might not be clear to modern readers how important Plotinus was. His Enneads, consisting of 54 essays, is an attempt for a world view that is going to exert great influence on medieval Islam and Christianity. In this work of Gerson, he continued the thinking he laid out in his <God and Greek Philosophy> where he pinpoints the central question Greek philosophers tried to answer: What is the ultimate cause and principle of explanation? In this way, the superiority of the Plotinian answer over that of Plato's and Aristotle's becomes clear. The reading in this book is very dense, but it is rewarding to me personally to see how studying of ancient Greek philosophy CAN be of value in the contemporary world in clarifying our own ideas and our implicit world view.
Without understanding Plotinus (and arguably Origen) and the anchor points, it is virtually impossible to understand and compare the various medieval philosophies from Augustine to Thomas Aquinas and Duns Scotus.