This article of CS Lewis was very difficult for me to understand mostly because of how deep he got into it and because of the length of the story. It seemed a little difficult to stay focused for the entire reading.
Subjectivism is the belief that individual persons or subjects are the source of knowledge and moral values. In this lecture that Lewis talks about how the subjectivist uses "practical reasoning" on everything in life. This practical reasoning is every action that we take in life whether it is a moral action or a physical action. This is what type of action we are going to take in each and every situation in life.
Lewis states that value judgments are not really judgments at all. They are sentiments, complexes, or attitudes produced in a community by the pressure of its environment and its traditions. The subject of subjectivism can be dangerous because it is bad for the human mind to invent new values. This is bad because you dont know how extreme the mind can take things. The moral values that we have come solely based on scripture.