The kind of logic discussed in this book is so different from the logic presented in school courses that they may seem to be two virtually unconnected subjects. There is a profound reason for this contradiction. It is rooted in the opposite positions taken by the academic and the Marxist schools of logic on the relations between thought and reality, more specifically, between logic and the external world. Formal logicians, despite other differences amongst themselves, assume or assert that logic is essentially sealed up in the mind and has no necessary and unbreakable connections with society and nature. At the very best they are ambiguous and evasive on this central philosophical question.