Programming languages researchers make a variety of different kinds of claims about the design of languages and related tools and calculi. Each type of claim requires different kinds of reasons and evidence to justify. Claims regarding the aesthetics or elegance of a design, or its effects on people, are especially tricky to justify because they are less strictly defined and are subject to change depending on the exact audience. In this essay, we take an interdisciplinary approach to this problem by drawing on the fields of argument theory and rhetorical analysis to argue that programming languages researchers can provide reasons for their claims about effects on people by providing descriptions of specific features of their systems that support their claim. In order to demonstrate this framework, we show several examples of how this is already being practiced in some programming languages research, and conclude by calling for authors to provide descriptive evidence to bolster such claims and to frame and strengthen other evaluation methods such as user studies.