Lewin was reluctant to provide a strictly scientific basis for the theories he developed, and felt that the influences affecting a group’s behavior could be expressed mathematically as ‘forces’ comparable to those in physics and mechanical engineering. Under different circumstances, these forces can either drive a person or a group towards a particular goal (a driving force) or prevent them from achieving that goal (a restraining force).
These physical and social factors act upon the ‘group field’ of the group, which as well as their goals and aspirations include their hopes, fears, needs, and motives. A person’s living space, which Lewin called ‘a field of experience’, is constantly adapting in response to external stimuli, shaping ideas, attitudes, and behaviors depending on the degree to how much external influences are internalized. From these ideas, Lewin developed a method of group field analysis to assess the effects on individual and group behavior in response to external stimuli.