Vertical and horizontal lines are the expression of two opposing force — Piet Mondrian

"The rhythm of relations of color and size makes the absolute appear in the relativity of time and space."

"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."

"It may be noted that in Neo-Plastic art the crucial thing is the right angel, that is, the right-angle lines. And not whether the position of the lines is vertical or horizontal.. .So it is possible to make very beautiful things while placing the lines in a diagonal position."

"..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."

"As you can see this is a composition of vertical and horizontal lines which will (in an abstract manner) have to express the idea of rising upwards, of magnitude. This is the same idea which used, for example, to be the guiding principle in the construction of cathedrals. Since only the manner of expression and not the representation has to express this general idea, I have not given any title. An abstract human mind will, of itself, receive the intended impression. I always confine myself to expressing the general."

"I believe that it is possible by means of horizontal and vertical lines, constructed consciously but not calculating, guided by a higher intuition and brought to harmony and rhythm – I believe that these fundamental aesthetic shapes – where necessary supplemented by lines in other directions or curved lines, make it possible to arrive at a work of art which is as strong as it is true. For anyone who sees more deeply, there is nothing vague about this; it is only vague for the superficial observer of nature. And chance must be as far removed as calculation. And for the rest it seems to me that it is necessary to keep breaking off the horizontal or vertical line: for if these directions were not countered by others, they would themselves come to signify something specific and thus human."