This chapter connects philosophy of ecology with two central issues in philosophy of science: what marks the real, and the nature of laws of nature. On the former, biological communities are the problem case. Are they anything more than the individual organisms of different species comprising them? Answering requires evaluation of community structure and dynamics, species distribution patterns, and how interspecific groups might assemble into communities. Individualists, for example, argue species distributions along environmental gradients overlap continuously and significantly, do not form discrete boundaries, and that communities are only real if such distinct boundaries exist. On laws, various challenges confront the idea of distinctively ecological laws: the relative paucity of predictive success in ecology, that its models and experimental results lack sufficient generality, that candidate laws are riddled with exceptions, and that ecosystems are too complex. Some philosophers argue that other properties thought to preclude a discipline from trading in laws – limited predictive accuracy and generality, not being exceptionless – should be jettisoned. Ecology, they argue, has uncovered regularities – Gause’s law of competitive exclusion and numerous allometries – possessing a kind of necessity and therefore meriting the “natural law.” These arguments are found wanting.

In this chapter, I look into one of controversial issues in population ecology: the ‘competitive exclusion principle’ or ‘No two species of similar ecology can coexist or can occupy the same ecological niche’. I build a simple system model to theoretically demonstrate that two competing species may or may not coexist, depending on the combinations of the model’s parameter values. I recognize four categories of parameter combinations, one of which ensures stable coexistence, whereas in the remaining three categories one species is always eliminated. I consider the likelihood of the occurrence of these four categories in a natural environment to contend that the coexistence is not only possible theoretically but would even be the norm among natural populations. I discuss the implication of this perception on the evolution of niche selection by species in natural situations.