 A thought collective is defined by Fleck as a community of persons mutually exchanging ideas or maintaining intellectual interaction (1935a, II.4). Members of that collective not only adopt certain ways of perceiving and thinking, but they also continually transform it—and this transformation does occur not so much “in their heads” as in their interpersonal space. It is easy to observe this phenomenon in everyday life. When a group of people speak about something important, they start to speak about things which would not cross their minds if they were alone and which they would not tell if they were in another group of people. There arises a thought style characteristic for that group. There also arises a certain collective mood which straightens up the ties among the group members and inclines them to act in a certain way.