This paper studies the formality of law and legal reasoning. It argues that, though the law (and its application) is indeed formal in that it does not take into account a significant number of considerations that should in principle be relevant for an all-things-considered decision, this is not to be explained on the basis of some ontology of rules (i.e., rules as exclusionary reasons), but upon the nature of legal discourse when viewed as a social practice. How the law is applied to particular cases, when substantive considerations not referred to by the rules are important enough to defeat their application to the case and questions of this kind are not answered by the legal material (which includes or might include rules, principles etc.), but by beliefs that underlie legal practice, beliefs about the world and its relation to human beings and society. Insofar as these beliefs have impact upon practices we recognise as legal they are termed "images of law." Legal reasoning cannot be understood without paying due attention to the nature and evolution of images of law.Rules should be sufficiently sensible and sufficiently straightforward so that anyone who so desires and is blessed with average powers of application may be able to understand, on the one hand the useful ends they serve, and on the other hand the actual necessities which have brought about their institution. (Weil 1995, 12) Then came the churches, then came the schools, then came the lawyers, then came the rules. (Mark Knopfler, Telegraph Road)