Commons, E. J. Trudeau, S. A. Stein, F. A. Richards, and S. R. Krause. Hierarchical complexity of tasks shows the existence of developmental stages. Developmental Review. 18, 18.:237-278, 1998. Antonio Damasio. The Feeling of What Happens. Harvest Books, 2000. D. Davidson. Inquiries into Truth and Interpretation. Oxfo