In What Is Called Thinking? Martin Heidegger, perhaps the most influential existentialist philospher of our time, seeks out the essential nature of the process of thinking. The theme of this book is that we learn to think only as we inquire into those matters that normally remain unquestioned concerning our everyday existence and our traditions. Heidegger begins by pointing out that we come to know what it means to think when we ourselves try to think. As he develops this theme it becomes evident that Heidegger conceives of thinking as something quite other than having opinions or ideas, even something different from logical reasoning or scientific analysis. One of his most startling assertions is that -science does not think.' Rather, he says, thinking is a demand or call made upon us to respond to what lies before us and to take it to heart. It is a response to questions that the nature of the world makes upon us as creatures of that world. To be truly human, therefore, is to think.