The great influence of the work of Henri Bergson on contemporary philosophy is only now becoming clear. Part of this renaissance in Bergsonism is due to Gilles Deleuze and Emmanuel Levinas, both of whom have acknowledged Bergson as an inspiration for their philosophy. Bergson's key philosophical concept is "duration", which encompasses both memory and life. "The Challenge of Bergsonism" analyses this central but complex concept through a close reading of one of Bergson's key works, "Matter and Memory", setting it in the broader context of Bergson's writings. The text explores how Bergsonism questions our ways of thinking, particularly the concept of reality, and ultimately demands a return to ethics. It also includes an English translation of Jean Hyppolite's highly influential essay, "Various Aspects of Memory in Bergson".