This book explains how Duns Scotus's concept of 'Haecceitas'—thisness, or individuation—represents an insufficiently recognized yet central aspect of Aristotelianism, namely its denial of and flight from 'the play of difference' that was a core aspect of Plato's philosophy. The difficulty, the author asserts, is that there has been historically an all too common tendency to read Plato through the distorting lens of Aristotle's view of him. The author further asserts that Aristotelianism has informed Neo-Platonism to the extent that it too becomes a corruption of Plato's thought, because of their common flight from Plato's 'difference-oriented' theory of forms. Throughout this work is a concern with the thinking of Derrida and Heidegger, especially in terms of their readings of the classical and medieval traditions.