The Cross of Duality provides a way of representing the relationships between two or more two pairs of opposites, such as A and not-A and B and not-B.

For instance, Carl Jung defined four psychological types, in two pairs of opposites. First, the rational and irrational denote the A-dimension, consisting of thinking and feeling and sensation and intuition. The B-dimension then groups thinking with sensation and feeling with intuition. These have sometimes been associated with masculine and feminine, respectively, although doing so is probably no longer appropriate.

If we then add Jung’s relating concepts of extrovert and introvert, the cross of duality becomes three dimensional. Katharine Cook Briggs and her daughter Isabel Briggs Myers have extended this psychological typography into four dimensions with their Myers-Briggs Type Indicator (MBTI). In principle, there is no limit to the number of dimensions.

Ken Wilber’s four-quadrants model—known as AQAL, short for “all quadrants, all levels”, which is short for “all quadrants, all levels, all lines, all states, all types”—is another two-dimensional example, the dimensions being interior and exterior and individual and social. The exterior quadrants are labelled ‘It’ and ‘Its’, while the individual and social interior quadrants are called ‘I’ and ‘We’, respectively.