"For Aristotelian physics the membership of an object in a given class was of critical importance, because for Aristotle the class defined the essence or essential nature of the object, and thus determined its behavior in both positive and negative respects."

“An attempt to improve intergroup relations has to face a wide variety of tasks. It deals with problems of attitude and stereotypes in regard to other groups and to one's own group, with problems of development of attitudes and conduct during childhood and adolescence, with problems of housing, and the change of the legal structure of the community; it deals with problems of status and caste, with problems of economic discrimination, with political leadership and with leadership in many aspects of community life. It deals with the small social body of a family, a club or a friendship group, with the larger social body of a school or a school system, with neighborhoods and with social bodies of the size of a community, of the state, a nation and with international problems.”

“The life space... includes both the person and his psychological environment. The task of explaining behavior then becomes identical with finding a scientific representation of the life space and determining the function which links the behavior to the life space. This function is what one usually calls a law... The novelist who tells the story behind the behavior and development of an individual gives us detailed data about his parents, his siblings, his character, his intelligence, his occupation, his friends, his status. He gives us these data in their specific interrelation, that is, as part of a total situation. Psychology has to fulfill the same task with scientific instead of poetic means.... The method should be analytical in that the different factors which influence behavior have to be specifically distinguished. In science, these data have also to be represented in their particular setting within the specific situation. A totality of coexisting facts which are conceived of as mutually interdependent is called a field. Psychology has to view the life space, including the person and his environment, as one field.”

“A certain area within a channel may function as a “gate”; the constellation of the forces before and after the gate region is decisively different in such a way that the passing or not passing of the unit through the whole channel depends to a high degree upon what happens in the gate region. This holds not only for food channels but also for the travelling of a news item through certain communication channels in a group, for movement of goods, and the social locomotion of individuals in many organizations.”

“One can ask two different kinds of questions with regard to the topics of study in psychology as well as in other sciences. One can ask for the phenomenal characteristics of psychological units or events, for example, how many kinds of feelings can be qualitatively differentiated from one another or which characteristics describe an experience of a voluntary act. Aside from this are the questions asking for the why, for the cause and the effect, for the conditional-genetic interrelations. For example, one can ask: Under which conditions has been a decision made and which are the specific psychological effects which follow this decision? The depiction of phenomenal characteristics is usually characterized as “description”, the depiction of causal relationships as “explanation.”

“In psychology one can begin to describe the whole situation by roughly distinguishing the person and his environment . Every psychological event depends upon the state of the person and at the same time on the environment, although their relative importance is different in different cases.”

“Do not in any way 'prove the rule,' but on the contrary are completely valid disproofs, even though they are rare, indeed, so long as one single exception is demonstrable.”