We wish to give a precise formulation of the intuitive concept: The degree to which the known facts (the evidence) support a given hypothesis.

On the side of Niels Bohr, not to mention a few other physicists, there is an honest acknowledgment of a difficulty in understanding Einstein's objection to the “completeness” of the Ψ-function description of the quantum phenomenon. Yet the weight which Bohr himself attaches to Einstein's insistence may indicate that if the latter's difficulty could be understood, then, through the cooperation of understanding physicists, another great accomplishment of unification might be obtained which would be as fruitful for the future as either or both the general theory of relativity and Bohr's statistical theory have been to the present.

The Wittgensteinian thesis that “the result of philosophy is not a number of ‘philosophical propositions,’ but to make propositions clear” has been given various interpretations by subsequent philosophers. Thus, for example, certain British philosophers have confined themselves to the analysis of colloquial language and have developed great skill in sophistical demonstrations intended to show that there is no such thing as a philosophical problem. Another group of philosophers considers language solely as a phenomenon of human behavior and attempts to clarify confusions and misunderstandings within language by utilizing the statistical techniques of contemporary behavior psychology. Still other philosophers, under the impact of logical positivism, have maintained that the clarification of propositions entails the construction of a language with precise rules of formation, transformation, and reference into which one could translate all the non-contradictory portions of ordinary spoken language.

In this paper we propose to characterize Chauncey Wright's empirical psychology, or “psychozoology” as he called it, from a methodological standpoint. By a methodological characterization of any science we mean an analysis of its structure as distinguished from its actual findings. We mean, for example, a description of the kind or type of variable and law in any science as distinguished from the actual particular content of any defined variable or discovered law. This distinction between variables and the laws which obtain between them is, as a matter of fact, itself a methodological description of the findings of science. Wright, it is true, did not discuss the subject matter of psychology from a methodological point of view, perhaps because he was involved in developing the body of knowledge itself. On the other hand, his discussions of physics and chemistry, areas in which the subject matter was well developed, took a methodological turn (9, pp. 201, 43–96). Regardless of Wright's own practice, however, the methodological implications of his contribution in actual theory to “empirical” psychology remain, and drawing these implications is one means by which we will show the significance of his work relative to the development of psychological concepts and laws. We will consider what specific ways his position is similar to, and different from, the later American functionalists' views on these matters and on the problem of causal interaction between physical and phenomenal events. Any similarity will perhaps gain in significance if, as it is further claimed, there is an actual historical influence of Wright on Dewey, the most noted functionalist.

Most handbooks on statistics and the theory of probability leave the reader in a mysterious tangle of mathematical rules for computing apparently arbitrarily chosen numerical functions. At first sight, then, a treatise on the Logical Foundations of Probability raises hopes that it will be a guide to clarity in these matters. These hopes are strengthened if the reader remembers that the author, Professor Rudolph Carnap of the University of Chicago, is noted for his thesis that philosophy is the study of the logic of science. On the other hand, a first glance into this book may discourage a reader who, though familiar with statistics, is not familiar with modern logic and its notation. For this reason particularly I shall try to give an account of this book that will enable the interested student to form some opinion of its usefulness to him.