The 1990s marked a move into the world of integral ideas for Wilber. According to commentators he stopped referring to his work as transpersonal, in favor of the term "integral", by the mid-1990s. Literature now confirms that he has shifted from transpersonal psychology to integral psychology. According to Brys & Bokor Wilber presented major parts of his integral approach in the years 1997-2000. The integral theory included a four quadrant model of consciousness and its development, whose dimensions were said to unfold in a sequence of stages or levels. The combination of quadrants and levels resulting in an all-quadrant, all-level approach. The theory also included the concept of holon, "a whole that is simultaneously part of some other whole", and holarchy, "hierarchical holons within holons". According to reviewers, the spiritual dimension was central to Wilber's integral vision.