Laboratory experiments and observation of external phenomena enable the natural sciences to proceed with measurement and the quantification of knowledge. Referring to this fact, one used to style these sciences as the exact sciences and to belittle the lack of exactitude in the sciences of human action.

Today nobody any longer denies that on account of the insufficiency of our senses measurement is never perfect and precise in the full sense of these terms. It is only more or less approximate. Besides, the Heisenberg principle shows that there are relations that man cannot measure at all. There is no such thing as quantitative exactitude in our description of natural phenomena. However, the approximations that measurement of physical and chemical objects can provide are by and large sufficient for practical purposes. The orbit of technology is an orbit of approximate measurement and approximate quantitative definiteness.

In the sphere of human action there are no constant relations between any factors. There is consequently no measurement and no quantification possible. All measurable magnitudes that the sciences of human action encounter are quantities of the environment in which man lives and acts. They are historical facts, e.g., facts of economic or of military history, and are to be clearly distinguished from the problems with which the theoretical science of action—praxeology and especially also its most developed part, economics—deals.

Deluded by the idea that the sciences of human action must ape the technique of the natural sciences, hosts of authors are intent upon a quantification of economics. They think that economics ought to imitate chemistry, which progressed from a qualitative to a quantitative state.1  Their motto is the positivistic maxim: Science is measurement. Supported by rich funds, they are busy reprinting and rearranging statistical data provided by governments, by trade associations, and by corporations and other enterprises. They try to compute the arithmetical relations among various of these data and thus to determine what they call, by analogy with the natural sciences, correlations and functions. They fail to realize that in the field of human action statistics is always history and that the alleged “correlations” and “functions” do not describe anything else than what happened at a definite instant of time in a definite geographical area as the outcome of the actions of a definite number of people.2  As a method of economic analysis econometrics is a childish play with figures that does not contribute anything to the elucidation of the problems of economic reality.

• 1J. Schumpeter, Das Wesen und der Hauptinhalt der theoretischen Nationalökonomie (Leipzig, 1908), pp. 606 ff.; W. Mitchell, “Quantitative Analysis in Economic Theory,” American Economic Review, XV, I ff.; G. Cassel, On Quantitative Thinking in Economics (Oxford, 1935); and a daily increasing flood of books and articles.
• 2Mises, Human Action, pp. 347 ff.

Radical empiricism rejects the idea that certain knowledge concerning the conditions of the universe is accessible to the minds of mortal men. It considers the a priori categories of logic and mathematics as assumptions or conventions, freely chosen on account of their convenience for the attainment of the kind of knowledge that man is able to acquire. All that is inferred by deduction from these a priori categories is merely tautological and does not convey any information about the state of reality. Even if we were to accept the untenable dogma of regularity in the concatenation and succession of natural events, the fallibility and insufficiency of the human senses makes it impossible to ascribe certainty to any a posteriori knowledge. We, human beings as we are, must acquiesce in this state of affairs. How things “really” are or may appear when looked upon from the vista of a superhuman intelligence, essentially different from the human mind as it works in the present aeon of cosmic history, is for us inscrutable.

However, this radical skepticism does not refer to praxeological knowledge. Praxeology too starts from an a priori category and proceeds by deductive reasoning. Yet the objections raised by skepticism against the conclusiveness of a priori categories and a priori reasoning do not apply to it. For, as must be emphasized again, the reality the elucidation and interpretation of which is the task of praxeology is congeneric with the logical structure of the human mind. The human mind generates both human thinking and human action. Human action and human thinking stem from the same source and are in this sense homogeneous. There is nothing in the structure of action that the human mind cannot fully explain. In this sense praxeology supplies certain knowledge.

Man as he exists on this planet in the present period of cosmic history may one day disappear. But as long as there are beings of the species Homo sapiens there will be human action of the categorial kind praxeology deals with. In this restricted sense praxeology provides exact knowledge of future conditions.

In the field of human action all quantitatively determined magnitudes refer only to history and do not convey any knowledge that would mean something beyond the specific historical constellation that generated them. All general knowledge, that is, all knowledge that is applicable not only to a definite constellation of the past but to all praxeologically identical constellations of the past as well as of the future, is deductive knowledge ultimately derived from the a priori category of action. It refers rigidly to any reality of action as it appeared in the past and will appear in the future. It conveys precise knowledge of real things.

According to an often quoted dictum of Auguste Comte, the objective of the—natural—sciences is to know in order to predict what will happen in the future. These predictions are, as far as they refer to the effects of human action, conditional. They say: If A, then B. But they do not tell anything about the emergence of A. If a man absorbs potassium cyanide, he will die. But whether he will swallow this poison or not is left undecided.

The predictions of praxeology are, within the range of their applicability, absolutely certain. But they do not tell us anything about the value judgments of the acting individuals and the way they will determine their actions. All we can know about these value judgments has the categorial character of the specific understanding of the historical sciences of human action. Whether our anticipations of—our own or other peoples’—future value judgments and of the means that will be resorted to for adjusting action to these value judgments will be correct or not cannot be known in advance.

This uncertainty of the future is one of the main marks of the human condition. It taints all manifestations of life and action.

Man is at the mercy of forces and powers beyond his control. He acts in order to avoid as much as possible what, as he thinks, will harm himself. But he can at best succeed only within a narrow margin. And he can never know beforehand to what extent his acting will attain the end sought and, if it attains it, whether this action will in retrospect appear—to himself or to the other people looking upon it—as the best choice among those that were open to him at the instant he embarked upon it.

Technology based on the achievements of the natural sciences aims at full control within a definite sphere, which, of course, comprehends only a fraction of the events that determine man’s fate. Although the progress of the natural sciences tends to enlarge the sphere of such scientifically directed action, it will never cover more than a narrow margin of possible events. And even within this margin there can never be absolute certainty. The result aimed at can be thwarted by the invasion of forces not yet sufficiently known or beyond, human control. Technological engineering does not eliminate the aleatory element of human existence; it merely restricts its field a little. There always remains an orbit that to the limited knowledge of man appears as an orbit of pure chance and marks life as a gamble. Man and his works are always exposed to the impact of unforeseen and uncontrollable events. He cannot help banking upon the good luck not to be hit by them. Even dull people cannot fail to realize that their well-being ultimately depends on the operation of forces beyond man’s wisdom, knowledge, prevision, and provision. With regard to these forces all human planning is vain. This is what religion has in mind when it refers to the unfathomable decrees of Heaven and turns to prayer.

Many data with which the mind is concerned either in retrospect or in planning for the future can be expressed in numerical terms. Other relevant magnitudes can only be put into words of a nonmathematical language. In regard to such magnitudes the specific understanding of the sciences of human action is a substitute, as it were, for the unfeasibility of measurement.

In this sense the historian as well as the acting man speaks of the relevance of different events and actions in regard to their production of other events and of definite states of affairs. In this sense they distinguish between more important and less important events and facts and between greater men and lesser men.

Misjudgments in this quasi-quantitative evaluation of reality are pernicious if they occur in planning actions. Speculations are bound to fail if based upon an illusory anticipation of future conditions. Even if they are “qualitatively” correct, i.e., if the conditions they have anticipated really appear, they may bring disaster if they are “quantitatively” wrong, i.e., if they have erred concerning the dimensions of the effects or concerning the timing of their appearance. It is this that makes the long-range speculations of statesmen and of businessmen especially hazardous.

In forecasting what may or will happen in the future, man can either be right or mistaken. But his anticipation of future events cannot influence the course of nature. Whatever man may expect, nature will go its own way unaffected by any human expectations, desires, wishes, and hopes.

It is different in the sphere in which human action can operate. Forecasting may prove mistaken if it induces men to proceed successfully in a way that is designed to avoid the happening of the forecast events. What impels people to listen to the opinions of soothsayers or to consult with them is frequently the desire to avoid the emergence of undesirable events that, according to these prophecies, the future has in store for them. If, on the other hand, what the oracle promised them agreed with their wishes, they could react to the prophecy in two ways. Trusting to the oracle, they could either become indolent and neglect doing what had to be done in order to bring about the end forecast. Or they could, full of confidence, double their effort to attain the goal desired. In all such cases the content of the prophecy had the power to divert the course of affairs from the lines that it would have pursued in the absence of an allegedly authoritative forecast.

We may illustrate the issue by referring to business forecasting. If people are told in May that the boom going on will continue for several months and will not end in a crash before December, they will try to sell as soon as possible, at any rate before December. Then the boom will come to an end before the day indicated by the prediction.

Economics can predict the effects to be expected from resorting to definite measures of economic policies. It can answer the question whether a definite policy is able to attain the ends aimed at and, if the answer is in the negative, what its real effects will be. But, of course, this prediction can be only “qualitative.” It cannot be “quantitative” as there are no constant relations between the factors and effects concerned. The practical value of economics is to be seen in this neatly circumscribed power of predicting the outcome of definite measures.

Those rejecting the aprioristic science of economics on account of its apriorism, the adepts of the various schools of Historicism and Institutionalism, ought from the point of view of their own epistemological principles to be prevented from expressing any judgment about the future effects to be expected from any definite policy. They cannot even know what a definite measure, whenever resorted to, brought about in the past. For what happened was always the result of the joint operation of a multitude of factors. The measure in question was only one of many factors contributing to the emergence of the final outcome. But even if these scholars are bold enough to assert that a definite measure in the past resulted in a definite effect, they would not—from the point of view of their own principles—be justified in assuming that therefore the same effect will be attained in the future too. Consistent Historicism and Institutionalism would have to refrain from issuing any opinion about the—necessarily future—effects of any measure or policy. They would have to restrict their teachings to the treatment of economic history. (We may pass over the question how economic history could be dealt with without economic theory.)

However, the public’s interest in the studies labeled as economic is entirely due to the expectation that one can learn something about the methods to be resorted to for the attainment of definite ends. The students attending the courses of the professors of “economics” as well as the governments appointing “economic” advisers are anxious to get information about the future, not about the past. But all that these experts can tell them, if they remain faithful to their own epistemological principles, refers to the past.

To comfort their customers—statesmen, businessmen, and students—these scholars have developed the trend doctrine. They assume that trends that prevailed in the recent past—inappropriately often dubbed the present—will also continue in the future. If they consider the trend as undesirable, they recommend measures to change it. If they consider it as desirable, they are inclined to declare it as inevitable and irresistible and do not take into account the fact that trends manifested in history can change, often or rather always did change, and may change even in the immediate future.

There are fads and fashions in the treatment of scientific problems and in the terminology of the scientific language.

What praxeology calls choosing is nowadays, as far as it concerns the choice of means, called decision-making. The neologism is designed to divert attention from the fact that what matters is not simply to make a choice, but to make the best possible choice. This means: to proceed in such a way that no less urgently desired end should be satisfied if its satisfaction prevents the attainment of a more urgently desired end. In the production processes directed in the market economy by profit-seeking business this is accomplished as far as possible with the intellectual aid of economic calculation. In a self-sufficient, closed, socialist system, which cannot resort to any economic calculation, the making of decisions concerning means is mere gambling.

In the natural sciences a theory can be maintained only if it is in agreement with experimentally established facts. This agreement was, up to a short time ago, considered as confirmation. Karl Popper, in 1935, in Logik und Forschung3  pointed out that facts cannot confirm a theory; they can only refute it. Hence a more correct formulation has to declare: A theory cannot be maintained if it is refuted by the data of experience. In this way experience restricts the scientist’s discretion in constructing theories. A hypothesis has to be dropped when experiments show that it is incompatible with the established facts of experience.

It is obvious that all this cannot refer in any way to the problems of the sciences of human action. There are in this orbit no such things as experimentally established facts. All experience in this field is, as must be repeated again and again, historical experience, that is, experience of complex phenomena. Such an experience can never produce something having the logical character of what the natural sciences call “facts of experience.”

If one accepts the terminology of logical positivism and especially also that of Popper, a theory or hypothesis is “unscientific” if in principle it cannot be refuted by experience. Consequently, all a priori theories, including mathematics and praxeology, are “unscientific.” This is merely a verbal quibble. No serious man wastes his time in discussing such a terminological question. Praxeology and economics will retain their paramount significance for human life and action however people may classify and describe them.

The popular prestige that the natural sciences enjoy in our civilization is, of course, not founded upon the merely negative condition that their theorems have not been refuted. There is, apart from the outcome of laboratory experiments, the fact that the machines and all other implements constructed in accordance with the teachings of science run in the way anticipated on the ground of these teachings. The electricity-driven motors and engines provide a confirmation of the theories of electricity upon which their production and operation were founded. Sitting in a room that is lighted by electric bulbs, equipped with a telephone, cooled by an electric ran, and cleaned by a vacuum cleaner, the philosopher as well as the layman cannot help admitting that there may be something more in the theories of electricity than that up to now they have not been refuted by an experiment.

• 3Now also available in an English-language edition, The Logic of Scientific Discovery (New York, 1959).

The epistemologist who starts his lucubrations from the analysis of the methods of the natural sciences and whom blinders prevent from perceiving anything beyond this field tells us merely that the natural sciences are the natural sciences and that what is not natural science is not natural science. About the sciences of human action he does not know anything, and therefore all that he utters about them is of no consequence.

It is not a discovery made by these authors that the theories of praxeology cannot be refuted by experiments nor confirmed by their successful employment in the construction of various gadgets. These facts are precisely one aspect of our problem.

The positivist doctrine implies that nature and reality, in providing the sense data that the protocol sentences register, write their own story upon the white sheet of the human mind. The kind of experience to which they refer in speaking of verifiability and refutability is, as they think, something that does not depend in any way on the logical structure of the human mind. It provides a faithful image of reality. On the other hand, they suppose, reason is arbitrary and therefore liable to error and misinterpretation.

This doctrine not only fails to make allowance for the fallibility of our apprehension of sense objects; it does not realize that perception is more than just sensuous apprehension, that it is an intellectual act performed by the mind. In this regard both associationism and Gestalt psychology agree. There is no reason to ascribe to the operation the mind performs in the act of becoming aware of an external object a higher epistemological dignity than to the operation the mind performs in describing its own ways of procedure.

In fact, nothing is more certain for the human mind than what the category of human action brings into relief. There is no human being to whom the intent is foreign to substitute by appropriate conduct one state of affairs for another state of affairs that would prevail if he did not interfere. Only where there is action are there men.

What we know about our own actions and about those of other people is conditioned by our familiarity with the category of action that we owe to a process of self-examination and introspection as well as of understanding of other peoples’ conduct. To question this insight is no less impossible than to question the fact that we are alive.

He who wants to attack a praxeological theorem has to trace it back, step by step, until he reaches a point in which, in the chain of reasoning that resulted in the theorem concerned, a logical error can be unmasked. But if this regressive process of deduction ends at the category of action without having discovered a vicious link in the chain of reasoning, the theorem is fully confirmed. Those positivists who reject such a theorem without having subjected it to this examination are no less foolish than those seventeenth-century astronomers were who refused to look through the telescope that would have shown them that Galileo was right and they were wrong.