The validity of certain critical reasoning steps carried out during or on the sidelines of the environmental science, public health survey, medical experiment, population risk assessment, or disease space-time mapping under conditions of in situ uncertainty and space-time heterogeneity, is often not given sufficient attention and may even be out of the investigator's line of thought. For example, the technical complexity of an environmental exposure experiment may overshadow the logical assumptions made when moving from one phase of the experiment to the next, or the study of population risk assessment may focus on analytical and computational matters, whereas methodological and cultural factors are neglected.This book helps health investigators structure their thinking so that they avoid logical mistakes and argument pitfalls, and also gain new insights about reality, improve their awareness of the environment and context within which one's thinking takes place.