Martin Heidegger's Being and Time is one of the world's most famous philosophical classics in the past 100 years, and it is also one of the most difficult philosophical works to read. One of the reasons why it is difficult to read or "unreadable" is that many readers do not know the status and significance of the second section in the whole book.

The purpose of this lecture is to emphasize and illustrate that the second section of Being and Time is the true beginning of the book. The problem consciousness of the whole book appears here, and its series of core concepts such as being (Sein), human existence (Dasein), the understanding of existence, the meaning of existence, hermeneutical cycle, etc., are also the first time to appear in a formal sense. Therefore, it is difficult to truly enter Heidegger’s Being and Time and even his philosophical system if you do not understand this section; ignoring this section will more or less deviate from Heidegger's problem direction, misunderstand or underestimate the philosophical significance of his Being and Time.