 Semantic inheritance networks differ from Pollock’s system in two important ways. First, they cannot represent one fact’s constituting an undercutting defeater of an inference, although they can represent rebutting defeaters. For example, they do not allow an inference from the apparent color of an elephant to its actual color to be undercut by the information that my color vision is unreliable, unless I have information about the actual color of the elephant that contradicts its apparent color. Secondly, they do incorporate the principle of specificity (the principle that rules with more specific antecedents take priority in case of conflict) into the very definition of a warranted conclusion. In fact, in contrast to Pollock, the semantic inheritance approach gives priority to rules whose antecedents are weakly or defeasibly more specific. That is, if the antecedent of one rule is defeasibly linked to the antecedent of a second rule, the first rule gains priority. For example, if Quakers are typically pacifists, then, when reasoning about a Quaker pacifist, rules pertaining to Quakers would override rules pertaining to pacifists. For the details of semantic inheritance theory, see the following supplementary document: