 For each configuration , let be the pattern consisting of the single symbol that appears at position zero of .By continuity of , there must exist a finite pattern in such that, if the positions outside are changed arbitrarily but the positions within are fixed to their values in , then the result of applying remains the same at position zero.Equivalently, there must exist a fundamental open set such that belongs to and such that for every configuration in , and have the same value at position zero.