July 1948 Constant founded Reflex "" with Corneille, Karel Appel and his brother Jan Nieuwenhuys. The first edition of the magazine "Reflex" was published with a manifesto written by Constant. For Constant art had to be experimental. He had deducted this from the French word 'expérience' and believed that art springs from experience of the artist and is continuously changing. In the manifesto he stated that the process of creation is more important to the experimental artist than the work itself; it is a means to reach spiritual and mental enrichment. Also, the work of experimental artists is a mirror image of changes in the general perception of beauty.