We speak of 'concrete' and not 'abstract painting', because we have finished with the period of research and speculative experience. In their search for purity artists were obliged to abstract from 'natural forms' in which the plastic elements were hidden, in order to eliminate natural forms and to replace them with 'artistic forms'. To-day the idea of 'artistic form' is as obsolete as the idea of 'natural form'. We establish the period of pure painting by constructing 'spiritual form'. Creative spirit becomes concrete.

In: 'Comments on the basic of concrete painting', Paris, January 1930; 'Art Concret', April 1930, pp. 2-4