Read this and answer the question

Most legal theorists believe that the rule of law has purely formal characteristics, meaning that the law must be publicly declared, with prospective application, and possess the characteristics of generality, equality, and certainty, but there are no requirements with regard to the content of the law. Others, including a few legal theorists, believe that the rule of law necessarily entails protection of individual rights. Within legal theory, these two approaches to the rule of law are seen as the two basic alternatives, respectively labelled the formal and substantive approaches. Still, there are other views as well. Some believe that democracy is part of the rule of law.

What are the two approaches to defining the concept of the rule of law?
formal and substantive