Abstract: “In order to appreciate the good, one must know the bad.” On 2 December 1917, Paul Smekens (1890-1983) gave a lecture with lichtbeelden (projected images) on modern architecture at the Vlaamsche Kring (Flemish Circle) in Mortsel. “The architecture of the nineteenth century was the negation of all originality. Fixed rules were set according to which each building had to be built in a certain style according to its purpose : churches in gothic style, town halls in renaissance style, etc. The society that is constantly progressing did not understand much about this art of plagiarism and did not bother at all. This art was outside living life. (.) The lecturer distinguishes in today’s architecture two directions : the one that is still under the influence of the XIXth century and is bad, and the one that has made itself free, and therefore good” . With lectures on modern architecture, avant-garde art, science, and commerce, the Vlaamsche Kring moralized with seemingly ‘neutral’ images and by using a comparative strategy of contrasting images of a seemingly neutral subject such as architecture, subtle activist messages were dispersed by an organisation that declared itself “independent of any political colour” . As such, it paved the way for the dissemination of radical politics in occupied Belgium during the First World War, supported by lantern slides as well as one of the major Flemish entrepreneurs of his time (and a producer of slides) Lieven Gevaert (1868-1935).