 Some versions of the a priori approach emphasize the constraints imposed by “thinner” moral concepts such as goodness, rightness, or morality itself (for example, see Garcia 1988). Once again, a defender of DMR might say that, if these concepts have enough content to preclude significant disagreement in their application, then it is likely that many societies do not apply them at all—a form of moral disagreement in itself. Another response would be to argue, following R.M. Hare (1981), that a formal analysis, for example in terms of a kind of prescriptivity, is plausible with respect to some thinner moral concepts, and that this is consistent with significant moral disagreements. However, the a priori critics question the adequacy of any such analysis. Much of this debate concerns the acceptability of formal versus material definitions of morality (see the entry on the  definition of morality).