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.