But when all circumstantial constraints are considered the curriculum designer finds he still has options left. It is his commitment to making these remaining choices in a defensible way that leads him to search for additional principles which are not natural, but man-made. The curriculum developer expects that these conventional principles will be accepted not as facts of life but as expressions of a shared view of the way life can and should be. Taken together, these natural and conventional principles pro-vide enough constraints to enable the decision maker to re-solve consistently issues that arise and to justify his decisions on the ground that anyone who acknowledged his principles would choose as he chose.