The book "Principles of Science: Science and Hypothesis, Value of Science, Science and Method" by Henry Poincaré is three separate works of the author, which together help to highlight the basic principles and problems of science. In Science and Hypothesis, Poincaré examines the process of creating hypotheses and their impact on scientific research. In "The Value of Science", the author discusses the importance of science for society and the development of mankind. "Science and Method" provides an insight into the methods of scientific research and argues for the necessity of using mathematics in scientific research. These works of Poincaré help the reader to better understand the nature and importance of science in the modern world.