Concept · Cognitive Bias: Informal fallacies of presumption
Circular reasoning (circulus in demonstrando)
Origin: Traditional Latin logic
Biological Parallel
Runaway sexual selection in peacocks creates self-reinforcing logic: peahens prefer elaborate tails because elaborate tails signal 'good genes,' yet the only gene being selected is the one for preferring elaborate tails. The trait validates itself through its own existence—Fisher's runaway process is biological circular reasoning that can drive traits to maladaptive extremes. The premise (good genes) becomes indistinguishable from the conclusion (tail preference), yet the loop persists for millennia.