 The Faithfulness Condition is a methodological principle rather than a metaphysical principle. Given a distribution on \(\{X, Y, Z\}\) in which X and Y are independent, we should infer that the causal structure is that depicted in  Figure 6,  rather than  Figure 8.  This is not because  Figure 8  is conclusively ruled out by the distribution, but rather because it is preferable to postulate a causal structure that implies the independence of X and Y rather than one that is merely consistent with independence.