Figure 1 (below) is a schematic summary of what Ken Wilber calls `the four quadrants' of existence: intentional, behavioural, cultural and social. These four quadrants are a summary of a data search across various developmental and evolutionary fields. He examined over two hundred developmental sequences recognized by various branches of human knowledge -- ranging from stellar physics to molecular biology, from anthropology to linguistics, from developmental psychology to ethical orientations, from cultural hermeneutics to contemplative endeavours -- taken from both Eastern and Western disciplines, and including premodern, modern, and postmodern sources (Wilber 1995b, 1996d). He noticed that these various developmental sequences all fell into one of four major classes -- the four quadrants -- and further, that within those four quadrants there was substantial agreement as to the various stages or levels in each. Figure 1 is a simple summary of this data search.