Some philosophers, drawing upon Immanuel Kant’s Critique of Pure Reason, have questioned the nature and limits of reason. By contrast, human reason plays a central role in libertarian thought. In the ordinary dictionary sense, human reason means simply “the ability of a healthy mind to think and make judgments, especially based on practical facts.”

In Human Action, Ludwig von Mises depicts reason as a universal quality common to all human beings, emphasizing that reason is “the mark that distinguishes man from animals and has brought about everything that is specifically human.” As all humans have the ability to reason, human logic can only proceed by reference to reason. Reason is the only basis on which we can conduct inquiry and endeavor to expand the frontiers of knowledge. As Mises explains: “Scientists are bound to deal with every doctrine as if its supporters were inspired by nothing else than the thirst for knowledge.”

Those who reject the universality of human reason attempt thereby to avoid grappling with its dictates. They reject conclusions that follow from “an irrefutable chain of reason” and brazenly promote their own unreasonable theories if they regard such theories as politically expedient. For example, critical race theorists argue that objective truth, reason, and rationality are simply cover for the imposition of European values on nonwhite people and should therefore be rejected by those who favor multiculturalism. Their answer to the accusation that critical race theories are unreasonable is that the very concepts of reason and rationality are Eurocentric, and they are therefore justified in rejecting them:

Because critical theory rejects reason, it cannot be questioned. Under this rubric, [Allen C.] Guelzo says, the only purpose of questions is to serve the interests of the oppressive class, and “any answer you come up with, which doesn’t speak in terms of some hidden structure of oppression, can simply be dismissed as part of the structure of oppression.”

Critical race theorists argue that rather than being universal, logic is determined by personal characteristics such as one’s race or sex. Therefore, they embrace polylogism, which Pierre Perrin defines as “an epistemological view based on the proposition that the logical structure of the mind is substantially different between different groups.”

Mises explains that “the main motive for the development of the doctrines of polylogism, historicism, and irrationalism was to provide a justification for disregarding the teachings of economics in the determination of economic policies.” Mises’s response to that is that

it is a poor makeshift to dispose of a theory by referring to its historical background, to the “spirit” of its time, to the material conditions of the country of its origin, and to any personal qualities of its authors. A theory is subject to the tribunal of reason only. The yardstick to be applied is always the yardstick of reason.

Mises shows that rejecting human reason is incompatible with human flourishing, economic progress, and civilization itself.

Murray Rothbard also argues that human reason “dictates to man his proper ends as well as the means for their attainment.” He emphasizes the distinctive quality of reason in understanding human nature: “And here we come to a vital difference between inanimate or even non-human living creatures, and man himself . . . man, ‘the rational animal,’ possesses reason to discover such ends and the free will to choose.” Rothbard grounds the natural law principles that underpin his theory of ethics in “reason and rational inquiry.”

Mises does not link reason in that way to natural law principles, arguing instead that “the teachings of utilitarian philosophy and classical economics have nothing at all to do with the doctrine of natural right. With them the only point that matters is social utility.” From a utilitarian perspective, the reason why people should not choose to go on a murderous rampage is not because it violates an alleged natural right to life but rather because such conduct is inimical to man’s ultimate desires: “If you satisfy your thirst for blood, you must forego many other desires. You want to eat, to drink, to live in fine homes, to clothe yourselves, and a thousand other things which only society can provide.” Nobody will achieve their life goals if everybody attacks each other with impunity.

Other libertarians who do not accept the natural rights philosophy, relying instead on these types of consequentialist or contractual explanations for human action, have questioned the link drawn by Rothbard between human reason and natural law principles. For example, Butler Shaffer asks:

How does one discover the content of these principles? How do we distinguish one person’s identification of a transcendent “moral principle” from another person’s expression of a private prejudice? Are the natural rights theorists doing anything more than projecting their subjective preferences onto the universe and then characterizing them as “eternal principles”?

Rothbard’s answer to that is that the content of natural rights is derived through reason. In The Ethics of Liberty, he argues:

One common, flip criticism by opponents of natural law is: who is to establish the alleged truths about man? The answer is not who but what: man’s reason. Man’s reason is objective, i.e., it can be employed by all men to yield truths about the world. To ask what is man’s nature is to invite the answer. Go thou and study and find out!

In this way, albeit from different philosophical foundations, both natural rights and utilitarian philosophers uphold the importance and indispensability of human reason. Human reason is universal, but its universal quality does not mean that all people have equal reasoning ability—it means that all people can reason. Nor does this mean that people are always reasonable or that they are never influenced by their emotions or irrational feelings, or that all reasonable opinions should be treated as objective and universal. Further, the claim is not that the process of reasoning will lead to perfection or omniscience or that people will never fall into error. To err is human. However, as Mises asserts: “Man has only one tool to fight error: reason.”

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By Mises