"The severe restrictions which Wundt placed on introspection also manifest themselves in the types of judgment that his experimental subjects were required to make. In accordance with the precept that internal perception can only become observation insofar as it is linked to controllable external stimuli, the introspective reports from his laboratory are very largely limited to judgments of size, intensity, and duration of physical stimuli, supplemented at times by judgments of their simultaneity and succession."

“Internal perception also fails as a method for scientific psychology. In the nature of the case, it must be casual and therefore unsystematic. It excludes all deliberate investigation, because as soon as it becomes aware of itself it turns into the self-observation that is open to all the well-known and valid criticisms. It is, indeed, the basis of a psychology of consciousness, in the sense that conscious processes must be perceived to be known, but for a science it is not enough.”

“Wundt sought to achieve was a rejuvenation of philosophical inquiry by new means, not the constitution of a completely new discipline.”

“Historical studies of the sciences tend to adopt one of two rather divergent points of view. One of these typically looks at historical developments in a discipline from the inside. It is apt to take for granted many of the presuppositions that are currently popular among members of the discipline and hence tends to view the past in terms of gradual progress toward a better present. The second point of view does not adopt its framework of issues and presuppositions from the field that is the object of study but tends nowadays to rely heavily on questions and concepts derived from studies in the history, philosophy, and sociology of science. A history written from the insider's point of view always conveys a strong sense of being "our" history. That is not the case with the second type of history, whose tone is apt to be less celebratory and more critical.”

“Psychological research on populations had a tendency to replace the social categories that defined populations in real life with populations defined in terms of nonsocial categories. American psychology aimed to be a socially relevant science, but not a social science. Its approach was to be that of a natural science, although its ultimate field of application was to be found among members of real societies.”

“Wundt initiated the first systematic psychological research programme. This achievement occurred at the same time as his elaboration of a philosophy of science which was anti-inductivist and stressed the priority of explanatory motives. Specifically psychological explanations depended on concepts of psychological causality as manifested in apperceptive or volitional processes. The major differences between the Wundtian and other models of psychological experimentation can be understood in the light of this general approach. Thus experimenters and subjects had to be enlightened collaborators and the role of introspection was more significant in an explanatory than in a purely observational context. Wundt's special requirements for the psychological experiment led him to reject other early models as exemplified by the hypnotic experiment in which the experimenter-subject relationship was closer to what was to become the norm in the twentieth century.”

“The term “introspective psychology” is misleading in that it covers a variety of diverging positions on the theory and practice of introspection. From the beginning there was a basic discrepancy between the British and the German philosophic tradition, the former relying more exclusively on introspection than the latter. Wilhelm Wundt’s advocacy and use of introspection was extremely circumscribed and essentially limited to simple judgments tied to external stimulation. During the first decade of the twentieth century some experimental psychologists, notably E. B. Titchener and the, greatly enlarged the scope of introspection, ushering in the brief vogue of “systematic introspection.” The latter never gained wide support in North America and was supplanted in Germany by developments that do not constitute “introspective psychology” in any precise sense.”