 With the notions of intensive and extensive we come upon a crucial distinction for Deleuze that is explored in Chapters 4 and 5 of Difference and Repetition. Extensive quantities, such as length, area or volume, are divisible. A volume of matter divided into two equal halves produces two volumes, each having half the extent of the original one. Intensive magnitudes, by contrast, refer to properties such as temperature or pressure that cannot be so divided. If a volume of water whose temperature is 90º is divided in half, the result is two volumes at the original temperature, not two volumes at 45º. However, the important property of intensity is not that it is indivisible, but that it is a property that cannot be divided without involving a change in kind. The temperature of a volume of water, for instance, can be “divided” by heating the container from below, causing a temperature difference between the top and the bottom. In so doing, however, we change the system qualitatively; moreover, if the temperature differences reach a certain threshold (if they attain a certain “intensity” in Deleuze’s terms), the system will undergo a “phase transition,” losing symmetry and changing its dynamics, entering into a periodic pattern of motion—convection—which displays extensive properties of size: X centimeters of length and breadth. Drawing on these kinds of analyses, Deleuze will assign a transcendental status to the intensive: intensity, he argues, constitutes the genetic condition of extensive space. Intensive processes are themselves in turn structured by Ideas or multiplicities.