"In addition, 'Elementarism' is real instead of abstract. The use of the term 'abstract' also caused much misunderstanding. This is easily explained.. .As used in connection with visual methods of expression, the term 'abstract' is extremely relative. 'To abstract' something implies one of those mental activities (in contrast to emotional spontaneity) through which certain [aesthetic] values are isolated from the world of reality. However, when such values were realized visually and applied as purely constructive means, they became real. Thus the abstract was transformed into the real, thereby illustrating the relativity of the former term. Hence, the term ‘abstract-real’ [proposed by his former artist-fellow Piet Mondrian,] was a fortunate invention, although in reference to a new orientation [van Doesburg's new art orientation 'Elementarism'] the term 'real' is sufficient. The period of abstraction is at an end. Is not an elementary painting, which is to say a certain composition of plane-linear colours, organic in itself, more concrete..."
January 1, 1970
https://en.wikiquote.org/wiki/Theo_van_Doesburg