[Excerpt] This article applies the concept of levels of abstraction to legal thinking. Perhaps the most important use of the concept is to constrain judicial lawmaking in a principled way. Level of abstraction refers to: the numbers of persons and transactions that generate an issue, the numbers of persons and transactions of which a piece of evidence is true, the numbers of persons and transactions to which an argument applies, and the numbers of persons and transactions that are affected by the resolution of an issue. In general, the more persons and transactions to which an issue and its resolution apply, the higher the level of abstraction of the issue and resolution; and the more persons and transactions of which a piece of evidence is true, or to which an argument applies, the higher the level of abstraction of the evidence.