Judicious rationalists do not pretend that human reason can ever make man omniscient. They are fully aware of the fact that, however knowledge may increase, there will always remain things ultimately given and not liable to any further elucidation. But, they say, as far as man is able to attain cognition, he must rely upon reason. The ultimate given is the irrational. The knowable is, as far as it is known already, necessarily rational. There is neither an irrational mode of cognition nor a science of irrationality.
With regard to unsolved problems, various hypotheses are permissible provided they do not contradict logic and the uncontested data of experience. But these are hypotheses only.
We do not know what causes the inborn differences in human abilities. Science is at a loss to explain why Newton and Mozart were full of creative genius and why most people are not. But it is by all means an unsatisfactory answer to say that a genius owes his greatness to his ancestry or to his race. The question is precisely why such a man differs from his brothers and from the other members of his race.
It is a little bit less faulty to attribute the great achievements of the white race to racial superiority. Yet this is no more than vague hypothesis which is at variance with the fact that the early foundations of civilization were laid by peoples of other races. We cannot know whether or not at a later date other races will supplant Western civilization.
However, such a hypothesis must be appraised on its own merits. It must not be condemned beforehand because the racists base on it their postulate that there is an irreconcilable conflict between various racial groups and that the superior races must enslave the inferior ones. Ricardo's law of association has long since discarded this mistaken interpretation of the inequality of men. It is nonsensical to fight the racial hypothesis by negating obvious facts. It is vain to deny that up to now certain races have contributed nothing or very [p. 90] little to the development of civilization and can, in this sense, be called inferior.
If somebody were eager to distill at any cost a grain of truth out of the Marxian teachings, he could say that emotions influence a man's reasoning very much. Nobody ever ventured to deny this obvious fact, and Marxism cannot be credited with its discovery. But it is without any significance for epistemology. There are many sources both of success and of error. It is the task of psychology to enumerate and to classify them.
Envy is a widespread frailty. It is certain that many intellectuals envy the higher income of prosperous businessmen and that these feelings drive them toward socialism. They believe that the authorities of a socialist commonwealth would pay them higher salaries than those that they earn under capitalism But to prove the existence of this envy does not relieve science of the duty of making the most careful examination of the socialist doctrines. Scientists are bound to deal with every doctrine as if its supporters were inspired by nothing else than the thirst for knowledge. The various brands of polylogism substitute for a purely theoretical examination of opposite doctrines the unmasking of the background and the motives of their authors. Such a procedure is incompatible with the first principles of ratiocination.
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. A theory is either correct or incorrect. It may happen that the present state of our knowledge does not allow a decision with regard to its correctness or incorrectness. But a theory can never be valid for a bourgeois or an American if it is invalid for a proletarian or a Chinese.
If the Marxians and the racist were right, it would be impossible to explain why those in power are anxious to suppress dissenting theories and to persecute their supporters. The very fact that there are intolerant governments and political parties intent upon outlawing and exterminating dissenters, is a proof of the excellence of reason. It is not a conclusive proof of a doctrine's correctness that its adversaries use the police, the hangman, and violent mobs to fight it. But it is a proof of the fact that those taking recourse to violent oppression are in their subconsciousness convinced of the untenability of their own doctrines.
It is impossible to demonstrate the validity of the a priori foundations [p. 91] of logic and praxeology without referring to these foundations themselves. Reason is an ultimate given and cannot be analyzed or questioned by itself. The very existence of human reason is a nonrational fact. The only statement that can be predicated with regard to reason is that it is the mark that distinguishes man from animals and has brought about everything that is specifically human.
To those pretending that man would be happier if he were to renounce the use of reason and try to let himself be guided by intuition and instincts only, no other answer can be given than an analysis of the achievements of human society. In describing the genesis and working of social cooperation, economics provides all the information required for an ultimate decision between reason and unreason. If man reconsiders freeing himself from the supremacy of reason, he must know what he will have to forsake. [p. 92]
 See below, pp. 158-163