Multiplicity (French: multiplicité) is a philosophical concept developed by Edmund Husserl and Henri Bergson from Riemann's description of the mathematical concept.[1] In his essay The Idea of Duration, Bergson discusses multiplicity in light of the notion of unity. Whereas a unity refers to a given thing in as far as it is a whole, multiplicity refers to the "parts [of the unity] which can be considered separately."[2] Bergson distinguishes two kinds of multiplicity: one form of multiplicity refers to parts which are quantitative, distinct, and countable, and the other form of multiplicity refers to parts that are qualitative, which interpenetrate, and which each can give rise to qualitatively different perception of the whole.[3]