Legal formalism is the foil for many theories of law. Yet formalism remains controversial, meaning that its critics focus on claims that are not central. This paper sets out a view of formalism using a methodology that embraces one of formalism’s most distinct claims, that formalism is a scientific theory of law. This naturalistic view of formalism helps to distinguish two distinct types of formalism, “doctrinal formalism,” the view that judicial behaviour can be represented using rules, and “rule formalism,” the (...) view that judges follow external rules when they are deciding cases. Doctrinal formalism, understood in naturalistic terms, overcomes many of the criticisms that have been levelled at formalism and can also be used to rehabilitate the currently out‐of‐favour “declaratory theory of law.” Doctrinal formalism is also a longstanding view of law, reflecting both what the original formalists thought of law, and what many present‐day doctrinal lawyers seem to believe. The naturalistic methodology is used to show that the main dispute between doctrinal formalism and American legal realism can be explained by a difference of assumptions concerning whether the values of judges are relative to society, or relative to other judges. (shrink)