Dissimilarity.

In order to form and make up a unity, in particular a creative unity, the individual conponents must needs be of different nature, they should even be in a sense contrasts. Two homogenous units will never be capable of forming a whole, or their whole at its best will remain barren. Man and woman become one, and physically and spiritually creative unity, by virtue of their dissimilarity. A hook and eye are a Unity, a fastening, but with two hooks you can do nothing. A right-hand glove with its contrast, the left-hand glove, makes up a whole, a pair of gloves; but two right-hand gloves you throw away. A number of perfectly similar objects do not make up a whole—a couple of cigarettes may quite well be three or nine. A quartet is a Unity because it is made up of dissimilar instruments. An orchestra is a Unity, and may be perfect as such, but twenty-double-basses striking up the same tune are Chaos.

- Isak Dinesen