Most ecologists are not card-carrying members of either individualistic or interdependent guilds, but our perception of plant community organization, and the way we conduct research, is affected by a historical dichotomy with lingering and powerful heuristic impacts; the dichotomy of the individualistic versus organismal nature of plant communities (Clements 1916, Gleason 1926). For example, the legacy of Gleason’s triumph lives on in almost all ecology textbooks, neutral theory (Hubbell 2001, Whitfield 2002) and assembly rules (see Lortie et al. 2004). The fundamental thesis of this book is that the current individualistic model is inadequate in the light of the last 20 years of empirical research on facilitation and indirect interactions. This is because these interactions demonstrate that plant communities frequently contain plant species that would not be present at all, or that would be present at much lower abundances, if it where not for the presence of other plant species (Callaway 1995, 1997).