 Reiter’s system is based on the use of default rules. A default rule consists of three formulas: the prerequisite, the justification, and the consequent. If one accepts the prerequisite of a default rule, and the justification is consistent with all one knows (including what one knows on the basis of the default rules themselves), then one is entitled to accept the consequent. The most popular use of default logic relies solely on normal defaults, in which the justification and the consequent are identical. Thus, a normal default of the form \((p\); \(q \therefore q)\) allows one to infer \(q\) from \(p\), so long as \(q\) is consistent with one’s endpoint (the extension of the default theory).