The aim of the article is to focus on the term “argument from desire”, which is often used by the scholars dealing with C. S. Lewis’s work, in order to answer the question if the term truly reflects the original thinking of the author. The first section briefly introduces the discussion of this topic in Czech and international titles. After that, we are going to describe the theme of Joy as related to Lewis’ notion of the word. The next section gives reasons why we think that the term “argument from desire” does not aptly illustrate the way the theme of desire and Joy is presented in Lewis’ work. Finally, the article discusses these topics from the perspective of fundamental theology and shows that Joy and desire should be rather seen as a part of Lewis’ personal testimony, which complements his rational arguments.