In this article the authors focus on how features of a computer-supported collaborative learning (CSCL) environment can elicit and support domain-specific reasoning and more specifically historical reasoning. The CSCL environment enables students to collaborate on a historical inquiry task and in writing an argumentative essay. In order to support historical reasoning the authors compared two representational tools: a graphical representation (argumentative diagram) and a linear representation (argument list). As it is assumed that an argumentative diagram can support both cognitive and interaction processes, it was expected that using this tool would result in more qualitative historical reasoning, in the chat as well as in the essay. However, the results of this study did not show a significant difference in the amount of historical reasoning between the two conditions. A possible explanation can be found in the way the students make use of the representational tool while executing the task. The tool does not only function as a cognitive tool that can elicit elaborate activities, but also as a tool through which students communicate. (Contains 7 tables and 3 figures.)