To the attention of readers is a book by the famous German philosopher and teacher Friedrich Paulsen (1846-1908), devoted to the analysis of the main issues of philosophy. In the first part of the book, the author considers the problems of metaphysics, which include ontological and cosmological-theological problems. The second part highlights the problems of knowledge theory - the problem of essence, or the relationship of cognition to reality, and the problem of the origin of cognition. Outlining philosophical problems in their development, the author not only cites their possible solutions proposed in the history of philosophy, but also seeks to justify the solution that seems correct to him. The paper also provides a brief overview of ethics issues. The book of F. Paulsen became so popular that only in Germany until 1914 withstood twenty-four editions; was repeatedly translated into many languages, including Russian.