In this handbook, Caroline Voet unravels the design principles of Dutch Benedictine monk and architect Dom Hans van der Laan (1904–1991). His ideas about spatial experience and proportions – in particular his unique discovery of the series of plastic numbers and the measurement system derived from it – have had a major influence and are still very much alive today. Step by step, Voet redraws Van der Laan’s philosophy of architectural space and links it to his proportional system of the plastic number in a series of clear, carefully constructed analyses.