"Instrumental" and "value rationality" are terms scholars use to identify two ways individuals act in order to optimize their behavior. Instrumental rationality recognizes means that "work" efficiently to achieve ends. Value rationality recognizes ends that are "right," legitimate in themselves. These two ways of reasoning seem to operate separately. Efficient means are recognized inductively in heads or brains or minds. Legitimate ends are felt deductively in hearts or guts or souls. Instrumental rationality provides intellectual tools—scientific and technological facts and theories—that appear to be impersonal, value-free means. Value rationality provides legitimate rules—moral valuations—that appear to be emotionally satisfying, fact-free ends. Every society maintains itself by coordinating instrumental means with value rational ends. Together they make humans rational. Sociologist Max Weber observed people exercising these capacities and gave them these labels that have stuck, despite scholars constantly coining new labels. Here are his original definitions, followed by a comment showing his doubt that humans are rational to believe that unconditionally right ends can be coordinated with conditionally efficient means. This article demonstrates the paradox of mutual contamination between instrumental and value rationality by reporting the reasoning of five scholars. Max Horkheimer linked instrumental reason with oppression. Harvard professors John Rawls and Robert Nozick, globally recognised as expert practitioners of value rationality, produced mutually incompatible theories of distributive justice. Neither is universally recognized as legitimate, but both continue to be defended as rational. Emory University professor James Gouinlock and Harvard professor Amartya Sen argued that Rawls and Nozick erred in believing that unconditionally valuable ends can work conditionally. Despite this disagreement, the scholarly community continues to accept as unavoidable this paradox of rationality contaminating itself. Max Horkheimer In "On the Critique of Instrumental Reason" and "Means and Ends", philosopher Max Horkheimer argued that instrumental rationality plays a key role in the oppressive industrial culture of capitalism. John Rawls Philosopher John Rawls accepted the reality of Weber's two kinds of rationality. He reasoned value rationally to identify unconditionally just patterns of social action capable of providing humans with a permanent instrumental moral compass. In two works, A Theory of Justice, published in 1971, and Justice as Fairness, published in 2002, he claimed to have identified one such pattern, valued both for its intrinsic legitimacy and its instrumental efficiency. Rawls did not use Weber's labels but made Weber's distinction. He relabeled social action “institutions” to identify rational patterns of socially prescribed behavior. He relabeled