Mathieu Schoenmaekers (1875–1944) is remembered as the philosopher behind the Dutch art movement De Stijl, made world famous by Piet Mondriaan. Here's a short account of how this happened: in 1910 the philosophically inclined Schoenmaekers (a former Catholic priest) came up with a new religious view. He called it Plastic mathematics or Positive mysticism, the word ‘positive’ meaning scientific.
Put simply, Schoenmaekers taught about an eternal superreality that's hidden behind ordinary everyday reality. This eternal world expresses itself in opposites. A bit like yin-yang. Schoenmaekers also taught that it was possible to take a scientific peek into this eternal mystical world by means of meditation on simple geometric figures and their symbolic meanings. Basically he would muse a lot about horizontal and vertical lines, circles and ellipses and he also wrote many, many books about his 'findings'. In a way you could think of him as Bucky Fuller's funny little nephew.
In search of disciples, Schoenmaekers joined a colony of artists and idealists in a little Dutch town called Laren. Here Schoenmaekers spent a lot of time with Piet Mondriaan and other De Stijl artists. Mondriaan bought his story and from that moment on had a clear new goal in his life: he wanted to express Schoenmaekers' eternal superreality in his paintings.
But this wasn't easy. Unlike the ancient Chinese inventors of yin-yang, who could spot this sort of thing everywhere they looked, Mondriaan felt that nature was always blocking his view, making it hard for him to see the eternal stuff clearly. Mondriaan concluded that nature was inferior and bad for the brain, and that it had to be destroyed. Only dead straight horizontal (yin) and vertical (yang) lines were acceptable in his paintings, like pure tools for enlightenment. Primary colors were kosher too. You could say Mondriaans paintings were his idea of heaven.
Piet Mondriaan was brought up in orthodox Dutch Calvinist style. The high pressure of this sort of environment seems to produce a steady stream of artistic diamonds as well as cramped minds. Anyway, with or without the help of Calvinism, the search for sacred art will continue and actually Mondriaan wasn't that mad compared with some of his colleagues.
Dutch road traffic signs and De Stijl
Because of the extreme flatness of Mondriaan's paintings and his exclusive use of 'pure' black, white, blue, red and yellow in his most important period, many people notice a resemblance between Mondriaan's paintings and road traffic signs. From a strictly Mondriaanesque point of view however, there is only one Dutch traffic sign that was designed following the aesthetic rules of De Stijl. Ironically, it's the sign for a dead end street :-) All other signs have either diagonal lines, circles or the wrong colors. I have no idea whether this is an intentional thing or a cosmic joke.
The Dutch Ministry of Transport and Public Works has a wonderful 80 page document called "Road Traffic Signs and Regulations 2009.pdf" for anyone who wants to check this dead end-theory.