Abstract Since the ancient rhetoricians, humans have awarded imagery, the visual, and the vivid an extraordinary effect on emotions and memory. Such assumptions have led to iconophobia, iconoclasm, and myths about the special power of images. The issue of the power of pictures, however, is more complicated. As all other kinds of rhetorical utterances, the visual can be both powerful and powerless depending on the circumstances. For many pictures, the rhetorical power lies not mainly in their political deliberation, but instead in their nature as demonstrative or epideictic rhetoric: a rhetoric that does not primarily advocate immediate change, but tries to increase adherence to existing view-points, attitudes and values. Even though visual rhetoric may perform a powerful address to those who are already convinced, it does not necessarily hold much power over adversaries and sceptics. This article argues that when teaching visuality and the power of imagery, educators ought to help young pupils – and the citizenry in general – not only to decode visual communication, but also to interpret and evaluate it. The first requires knowledge about rules of visual literacy, the second requires not only critical thinking, but also situational and cultural knowledge, as well as sound judgment.