 Thus, for developmental systems theory, many of the most widely applied, asymmetric and entirely legitimate distinctions biologists draw (between, say, genetic factors that create potential and environmental factors that select outcomes or genetic factors of determination and environmental factors of realisation) obtain their legitimacy from the conceptual clarity and specificity with which they are applied, not from their having tapped a profound and irreducible ontological truth about biological causation.One problem might be solved by reversing the direction of causation correctly identified in another.This parity of treatment is especially important when comparing the evolutionary and developmental explanations for one and the same character of an organism.