The Nature of Order is Christopher Alexander's four-volume work on what makes built form alive. The first volume, The Phenomenon of Life, is where he sets out the framework of 15 geometric properties that recur, in different combinations and intensities, in everything that feels alive. Alexander spent decades looking at buildings, towns, plants, animals, mountains, paintings, and carpets, and recording which qualities appeared in the things that felt most alive and which appeared in the things that felt least. The diagram is a translation of these properties into a single reference sheet.