They [Mondrian's friends in Paris, Tonia and Wim Stieltjes] are receptive to the new, although they do not know what it is. Thus I do occasionally fe… - Piet Mondrian

You should remember that my things are still intended to be paintings, that is to say, they are plastic representations, in and by themselves, not part of a building. Furthermore, they have been made in a small room. Also, that I use subdued colours for the time being, adapting myself to the present surroundings and to the outer world; this does not mean that I should not prefer a pure colouring. Otherwise you might think that I contradict myself in my work.

..the universal cannot be expressed purely so long as the particular obstructs the path. Only when this is no longer the case can the universal consciousness (intuition, that is) which is at the origin of all art, be rendered directly, giving birth to a purified art expression.
This, however, cannot appear before its proper time. For it is the spirit of the times that determines artistic expression, which, in turn, reflects the spirit of the times. But at the present moment, that form of art alone is truly alive which expresses our present - or future - consciousness.

[the double line in his paintings] is still one line, as in the case of your grooves [= the wide sunken lines in the relief's, the artist Gorin made then].. .In my last things the double line widens to form a plane, and yet it remains a line. Be that as it may, I believe that this question is one of those which lie beyond the realm of theory, and which are of such subtlety that they are rooted in the mystery of 'art'. But all that is not yet clear in my mind.