^1. S. Freud. The Future of an Illusion, New York, 1928. Civilization and its Discontents, New York, 1930. Neue Folge der Vorlesungen zur Einführung in die Psychoanalyse, Vienna, 1933. The “Neue Folge” is also now available in English.

^2. Early criticisms of Freud from moral and ethical standpoints are, of course, not worth considering at all. Today even some scientific criticisms of Freud like Knight Dunlap's (Freudism, Mysticism and Scientific Psychology, St. Louis, 1920) or even W. McDougall's (Outlines of Abnormal Psychology, New York, 1926) more carefully considered criticism seem somewhat ridiculous. My own very limited clinical experience has convinced me that the Freudian mechanisms exist and operate under existing environmental conditions in very much the way Freud claims they do.

^3. Cf. K. Lewin, The Conflict Between Aristotelian and Galileian Modes of Thought in Contemporary Physics and Biology. Jl. of Gen. Psych., 5, 141–177, 1931, and R. Carnap, “Die physikalische Sprache als Universalsprache der Wissenschaft,” Erkenntnis, 2, 432–465, 1931. Also O. Neurath, “Soziologie im Physikalismus,” the same 393–431, and H. Feigl, “The Mind-Body Problem” to be published in “Philosophy of Science.” Although Lewin and Carnap and his followers disagree on certain points they are working in the same direction. It would take us far beyond the limits set for this paper to go into these differences here.

^4. For the idea of “vergleichende Wissenschaftslehre” see K. Lewin, Ideen and Aufgabe einer vergleichenden Wissenschaftslehre. By “class” theory I mean essentially what Lewin has called Aristotelian theory, and by “field” theory what Lewin has called Galileian theory. Similarly Bertalanffy (Theoretische Biologie, I, p. 26, Berlin, 1932) speaks of “vorkopernikanische” and “nachkopernikanische” periods in the development of sciences. I prefer the designations “class” and “field” for the following reasons. The biological sciences, particularly psychology and sociology, make use even today of concepts which are primarily “class” concepts and all of the implications of “field” theory became clear only very recently. Although the “field” idea is implicit in Galileo and Newton it does not become explicit until the time of Clerk Maxwell. I find my students for this reason become somewhat confused by the designation “Aristotelian” and “Galileian.” Despite this change in nomenclature my very heavy debt to Prof. Lewin will be obvious to those of my readers, who have also read his theoretical papers.

^5. The Structure and Meaning of Psychoanalysis, New York, 1931.

^6. Civilization and its Discontents, p. 102.

^7. The Ego and the Id, 1923 and in the most of the subsequent writings; most recently, New Introductory Lectures, Lecture XXXI.

^8. Healy, Bronner, Bowers, pp. 2–6.

^9. In fairness, it must be said that Freud himself realizes the inadequacy of his theory of urges. In the New Lectures (p. 131) he says: “Die Trieblehre ist sozusagen unsere Mythologie. Die Triebe sind mythische Wesen, grossartig in ihrer Unbestimmtheit.

^10. E. Cassirer, Substanzbegriff und Funktionsbegriff, Berlin, 1910. Under substantial and functional Cassirer also includes or implies most of the other criteria which I set up.

^11. J. F. Brown, A Methodological Consideration of the Problem of Psychometrics. Erkenntnis, 1934, (in print).

^12. Cf. Lewin, The Conflict, etc., op. cit.

^13. Ordering phenotypical experience to genotypical constructs (Lewin) may also be expressed (with some reservations, cf. above) as translating “Protokolsprache” into “Physikalischesprache” (Carnap) or as translating the language of data into the language of constructs (Feigl). Cf. the references given above to these writers. Phenotypes, according to Lewin, represent experience; genotypes, the underlying dynamic situation. Cf. Lewin, Gesetz und Experiment in der Psychologie, Berlin-Schlachtensee, 1927.

^14. Cf. K. Lewin, Die Grundlagen der dynamischen Psychologie, Leipzig, to be published in 1934. I am indebted to Prof. Lewin for allowing me the use of the manuscript of his book.

^15. Op. cit., p. xx.

^16. H. Dingler, Der Zusammenbruch der Wissenschaft, etc., Munich, 1926. Cf. also J. F. Brown, op. cit.

^17. New Introductory Lectures.

^18. Cf. his own description of his early struggle in, “A History of the Psychoanalytical Movement,” New York, 1916.

^19. Cf. “Civilization and its Discontents,” and “The Future of an Illusion” for striking examples of this point.

^20. McDougall, op. cit. It is interesting that McDougall's use of purpose, Freud's use of libido, and Aristotle's entelechy are all “class” concepts, however.

^21. See the forthcoming book of Lewin, “Die Grundlagen der dynamischen Psychologie” and the series of papers by him and his students appearing in Psychol. Forsch. I hope in the near future to publish some studies on problems of psychopathology, which show the applicability of the field theory to abnormal as well as normal mental phenomena.