The surface of things gives enjoyment, their interiority gives life. - Piet Mondrian

the Cubists in Paris made me see that there was also a possibility of suppressing the natural aspect of form. I continued my research by abstracting the form and purifying the colour more and more. While working, I arrived at suppressing the closed effect of abstract form, expressing myself exclusively by means of the straight line in rectangular opposition; thus by rectangular planes of colour with white, grey and black. At that time, I encountered artists with approximately the same spirit, First Van der Leck, who, though still figurative, painted in compact planes of pure colour. My more or less cubist technique - in consequence still more or less picturesque - underwent the influence of his exact technique. Shortly afterwards I had the pleasure of making the acquaintance of Van Doesburg. Full of vitality and zeal for the already international movement that was called 'abstract', and most sincerely appreciative of my work, he came to ask me to collaborate in a review he intended to publish, and which he [Theo van Doesburg] was to call 'De Stijl'. I was happy with an opportunity to publish my ideas on art, which I was engaged in writing down: I saw the possibility of contacts with similar efforts.

I believe that in our period it is definitely necessary that, as far as possible, the paint is applied in pure colours, set next to each other in a pointillist or diffuse manner. This is stated strongly, and yet it relates to the idea which is the basis of meaningful expression in form, as I see it. It seems to me that the clarity of ideas should be accompanied by a clarity of technique.

Gradually I became aware [c. 1914-1918] that Cubism did not accept the logical consequences of its own discoveries; it was not developing abstraction towards its ultimate goal: the expression of pure reality.