Concept · Cognitive Bias: Informal fallacies of presumption
No true Scotsman
Origin: Flew, 1975
Biological Parallel
Ring species expose taxonomy's 'no true Scotsman' problem: salamanders around California's Central Valley interbreed with neighbors in a continuous ring, yet the populations at the ring's endpoints cannot interbreed. What defines the species? Each redefinition to exclude inconvenient intermediates creates new contradictions. Biology resolved this not by perfect criteria but by accepting that species boundaries are human constructs imposed on continuous variation. When definitions fail, the problem may be the definition, not the data.