Argumentative thinking requires not only the "skill" to apply argumentative strategies such as supporting theories with evidence but also the "will" to apply these strategies by considering argumentative thinking to be both reasonable and worthwhile. Focusing on direct instruction for the initial acquisition of both skill and will, we developed a new short-term computer-based training intervention. We tested its effects on learning processes and learning outcomes in an experimental study with 147 German high school students. Our intervention fostered facets of both skill (i.e. a declarative knowledge about argumentation) and will (i.e., epistemic orientation, intellectual values, and epistemic knowledge). We gained additional insights into learning mechanisms, such as the mediating effects of the learners' self-explanation activities and the advantage of addressing will before skill.