  Skepticism about moral reality is, thus, a reason for skepticism with moral falsehood, as developed by Mackie (1977), or skepticism about moral truth-value, as developed by Joyce (2001). Opponents of such error theories often object that some moral beliefs must be true because some moral beliefs deny the truth of other moral beliefs. However, error theorists can allow a negative moral belief (such as that eating meat is not morally wrong) to be true, but only if it merely denies the truth of the corresponding positive moral belief (that eating meat is morally wrong). If such denials of moral beliefs are not substantive moral beliefs (as denials of astrological beliefs are not astrology), then error theorists can maintain that all substantive moral beliefs are false or neither true nor false.