Science and what science is is one of the most challenging topics among modern thinkers. In his book "What is Science", Alan Francis Chalmers discusses the nature and nature of scientific methods based on inductiveism, falsificationism, rationalism, relativism, regression theories, and horizonism. In his other book, " Science and its Fabrication ", he tries to defend the objectivity of scientific knowledge by expressing positivist theory and historical − sociological strategy; But the findings suggest that Chalmers has drawbacks in explaining what science is in his first work. Although he has tried to eliminate them in his second book; But since his intellectual foundations are derived from Kant's theory and consequently Kant and positivist foundations, he could not combine the nature and construction of science and succeeded in explaining what science is. The author seeks to answer the question, what is science from the point of view of Alain Francis Chalmers, and what is the evolution of his reading of science? In the present article, first, the principles of Chalmers's thought in the two mentioned works have been studied by internal critique method and then external critique has been made by using Hamid Parsania's views. Professor Parsania, in order to get out of the crisis of the nature of science, considers it to have an intrinsic identity and soul that enters the second and third worlds with motives and contexts and is not limited to testable knowledge. In the present article, using the explanation of physicality, occurrence and spirituality, the survival of science and knowledge, the answer to Chalmers's problems in what science is has been explained.