Between 1920 and 1991, the Dutch Benedictine monk and architect Dom Hans van der Laan (1904–1991) developed his own proportional system. Just as the Benedictine monk Dom Mocquereau (1849–1930), in the beginning of the 20th century, defined a universal notational system to restore Gregorian chant, called “le nombre musical,” Van der Laan set out to develop a universal ordering system to restore architecture: “le nombre plastique” (the plastic number). Strangely enough, this “plastic number” did not entail a number, but a series of numbers based on the ratio 1.3247 … approximated as 4:3. According to Van der Laan, this ratio grew directly from discernment, the human ability to differentiate sizes, and as such would be an improvement over the golden ratio. To put his theories to the test, Van der Laan developed an architectural language, which can best be described as elementary architecture.

His oeuvre of only four convents and a house is published on an international scale (Fig. 1). They have become pilgrimage sites for practicing architects and members of various institutions who want to study and experience his spaces. His 1977 book De Architectonische ruimte: Vijftien lessen over de dispositie van het menselijk verblijf (Architectonic Space: Fifteen Lessons on the Disposition of the Human Habitat), translated into English, French, German and Italian, inspires many architects still today, as does his biography Modern Primitive, written in 1994 by the architect Richard Padovan, who had earlier translated De Architectonische ruimte into English.

To critically evaluate the plastic number and Van der Laan's theory of architectonic space, it is necessary to address the problem of the mythical image that Van der Laan created for himself. Van der Laan believed that architecture produced meaning through its affective qualities, and he saw his proportional system as an essential contribution to producing such meaning. Indeed, beyond presenting his plastic number as a design tool, Van der Laan aimed to elevate it to the status of a philosophical principle, and this aim dominated almost all of his writings. The Belgian philosopher André Van de Putte described Architectonic Space as philosophical as well as phenomenological poetics.