A number of theories on the development of human consciousness have tried to incorporate all views on the subject into one integral theory. However, Ken Wilber is the first philosopher who managed to combine the external with the internal fields of study. Using Wilber’s integral theory, a number of researchers developed their own theories in their field of speciality. Jim Marion used Wilber’s development theory to show the evolution of consciousness from a Christian perspective. Steve McIntosh, an integral philosopher, takes Wilber’s ideas further, and even criticises him on a few points. Another important researcher following Wilber is Andre Marquis, who developed an integral questionnaire to help pastors gauge clients’ problems. James Fowler, Clare Graves and Bill Plotkin also researched the evolution of human consciousness. This article examines each of these researchers, and concludes with a glance at several viewpoints on the soul and the mystical union with God.