After having passed through the various phases of plastic creation [the phases of arrangement, composition, and construction] I have arrived at the c… - Theo van Doesburg

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.

The work of art should be entirely conceived and formed by the mind before its execution. It should receive nothing from Nature’s formal properties or from sensuality or sentimentality.. .The picture should be constructed entirely from purely plastic elements, that is to say, planes and colours. A pictorial element has no other significance than 'itself', and therefore the picture has no other significance than 'itself'.

Had optical perception not evolved into something more than sensory perception, into super-sensory perception, then the present period would never have had the courage to discover the spiritual in matter. There would have been no fundamental difference between a painting by Picasso [from Picasso's so-called 'abstract' period] and one by Paulus Potter [Dutch painter from the 17th century, famous for his painting of cows]