I remained there [in The Netherlands, 1914-18] for the duration of the war, continuing my work of abstraction in a series of church. facades, trees, houses, etc. But I felt that I still worked as an Impressionist and was continuing to express particular feelings, not pure reality. Although I was thoroughly conscious that we can never be absolutely 'objective', I felt that one can become less and less subjective, until the subjective no longer predominates in one's work. More and more I excluded from my painting all curved lines, until finally my compositions consisted only of vertical and horizontal lines which formed crosses, each separate and detached from the other. Observing sea, sky and stars, I sought to indicate their plastic function through a multiplicity crossing verticals and horizontals.