I have tried in this book to present a comprehensive overview of science. As an activity, science can be considered at three, interdependent levels. At the first level is the individual investigator who makes observations, formulates hypotheses, and so forth. At the second level is the scientific collective that first recruits and then instructs the individual investigator in the appropriate ways of doing science and subsequently keeps the investigator's work under constant evaluation. At the third level, finally, is daily life, which provides the subject matter for scientific investigation and continuously influences and is influenced by science.