The "Convince Me" computer environment supports critical thinking by allowing users to create and evaluate computer-based representations of arguments. This study investigates theoretical and design considerations pertinent to using "Convince Me" as an educational tool to support reasoning about public policy issues. Among computer environments designed to support argumentation, "Convince Me" is unique in that it computes a measure of an argument's coherence and presents this information to users as feedback. This measure is based on the "ECHO" computational model, a connectionist implementation of the Theory of Explanatory Coherence. The study seeks to better understand this coherent argumentation measure by comparing it to other measures including a measure of the stability of one's views and the number of statements in an argument. Ten 17-year-old students and one scientist used "Convince Me" to create arguments about policies designed to ameliorate global warming; they also participated in pre- and post-intervention surveys and interviews. Positive correlations were found among the coherent argumentation measure, measures of stability, and number of statements in an argument, and these findings raise considerations for designing educational activities with "Convince Me". A debriefing interview's results illustrate further considerations, including the role of the user's stance towards the software.(Contains 2 figures and 4 tables.)