4. The A Priori Representation of Reality

No thinking and no acting would be possible to man if the universe were chaotic, i.e., if there were no regularity whatever in the succession and concatenation of events. In such a world of unlimited contingency nothing could be perceived but ceaseless kaleidoscopic change. There would be no possibility for man to expect anything. All experience would be merely historical, the record of what has happened in the past. No inference from past events to what might happen in the future would be permissible. Therefore man could not act. He could at best be a passive spectator and would not be able to make any arrangements for the future, be it only for the future of the impending instant. The first and basic achievement of thinking is the awareness of constant relations among the external phenomena that affect our senses. A bundle of events that are regularly related in a definite way to other events is called a specific thing and as such distinguished from other specific things. The starting point of experimental knowledge is the cognition that an A is uniformly followed by a B. The utilization of this knowledge either for the production of B or for the avoidance of the emergence of B is called action. The primary objective of action is either to bring about B or to prevent its happening.

Whatever philosophers may say about causality, the fact remains that no action could be performed by men not guided by it. Neither can we imagine a mind not aware of the nexus of cause and effect. In this sense we may speak of causality as a category or an a priori of thinking and acting.

To the man anxious to remove by purposive conduct some uneasiness felt, the question occurs: Where, how, and when would it be necessary to interfere in order to obtain a definite result? Cognizance of the relation between a cause and its effect is the first step toward man’s orientation in the world and is the intellectual condition of any successful activity. All attempts to find a satisfactory logical, epistemological, or metaphysical foundation for the category of causality were doomed to fail. All we can say about causality is that it is a priori not only of human thought but also of human action.

Eminent philosophers have tried to elaborate a complete list of the a priori categories, the necessary conditions of experience and thought. One does not belittle these attempts at analysis and systematization if one realizes that any proposed solution leaves a broad margin for the individual thinker’s discretion. There is only one point about which there cannot be any disagreement, viz., that they all can be reduced to the a priori insight into the regularity in the succession of all observable phenomena of the external world. In a universe lacking this regularity there could not be any thinking and nothing could be experienced. For experience is the awareness of identity or the absence of identity in what is perceived; it is the first step toward a classification of events. And the concept of classes would be empty and useless if there were no regularity.

If there were no regularity, it would be impossible to resort to classification and to construct a language. All words signify bundles of regularly connected acts of perception or regular relations among such bundles. This is valid also of the language of physics, which the positivists want to elevate to the rank of a universal language of science. In a world without regularity there would not be any possibility of formulating “protocol sentences.”7  But even if it could be done, such a “protocol language” could not be the starting point of a science of physics. It would merely express historical facts.

If there were no regularity, nothing could be learned from experience. In proclaiming experience as the main instrument of acquiring knowledge, empiricism implicitly acknowledges the principles of regularity and causality. When the empiricist refers to experience, the meaning is: as A was in the past followed by B, and as we assume that there prevails a regularity in the concatenation and succession of natural events, we expect that A will also in the future be followed by B. Therefore there is a fundamental difference between the meaning of experience in the field of natural events and in the field of human action.

• 7About the “protocol language,” cf. Carnap, “Die physikalische Sprache als Universalsprache der Wissenschaft,” Erkenntnis, II (1931), 432-65, and Carnap, “Uber Protokollsätze,” Erkenntnis, III (1932/33), 215-28.