 This point is “the closest that [Wimsatt] will come to a definition” (1976a: 209), and requires some explanation. The idea is roughly that patterns and regularities that can be used as a basis for prediction and explanation are found clustered around certain scales, and such clusters indicate levels of organization. Thus, if we plot regularity and predictability against (size) scale, then levels of organization will appear as peaks in the plot (see Figure). The entities that we find at these “local maxima” will exhibit stable regularities in virtue of the criteria (size, rate, dynamic properties, etc.) with which they are grouped into levels, and these regularities can also serve as the basis for reliable predictability. Moreover, levels of organization comprise “the most probable states of matter” (1976a: 239), meaning that if we could vary the initial conditions, under a range of conditions natural selection or other selection processes would result in the same levels (Wimsatt 1976a: 238–239). For example, if the level of molecules is a level of organization in Wimsatt’s sense, then there should be a peak in regularity and predictability at the scale(s) where molecules are located, and molecules should be the most probable mode of organization of matter under a range of conditions. 