Differentiation or alterity – often expressed as "the other" – are terms that have been a preoccupation for much of French philosophy during the second half of the twentieth century. A number of scholars have attributed the theme of otherness – with both its positive and negative connotations – to the combined influence of G.W. Hegel, Edmund Husserl and Martin Heidegger (e.g., Schrift 2006; Baugh 2003). Different philosophers will, of course, make somewhat idiosyncratic appropriations and combinations in their particular interpretations of the mode of otherness, thus preventing any cohesive definition or consistent usage of its terminology – though indeed certain overlaps do occur. All of the philosophers who feature in this volume have engaged with variant understandings of the idea of otherness.