St. Thomas Aquinas wrote a work called The Summa Theologica, and it's a systematic treatment of theology, and it treats a lot of different parts of human life in the rubric of theology. And one of the many topics in human life that Thomas talks about is law. So, he thinks that the ideal law is an ordinance of reason directed at the common good, made by the community or someone in due care of it, and it's promulgated. And he understands that there can be borderline laws that have some, but not all these features. One example would be: imagine a law that is just, it's ordered toward the common good, but the people in charge have done a bad job of posting notice of it. So that would be a law that is an ordinance of reason, directed to the common good. It's been made by the right people, but if they haven't posted it clearly, it's not so well promulgated. So it's law in three of the four senses, but it's not law in the fourth sense. More controversially, what about a law that's grossly unjust? And Thomas's definition of law leaves it ambiguous how unjust a law needs to be before it ceases to be law in any case whatsoever. Thomas's account of law is a teleological account. Teleology means the idea that some object has an end, and there are lots of objects that we recognize readily have ends. A paper clip is an object with an end. It has the end of holding together paper. And when objects have ends like this, the end gives the somebody who is working with the object a built in standard to know whether you're dealing with an excellent version of the object, an inferior version of the object, or something that even if someone claims it's an instance of the object, it's just a preposterous example of the object. Now that same way of thinking can apply to human life too. It does apply with a lot more controversy. But if you stipulate that this other approach applies to human life, then people have ends. And in the natural law tradition, people have the end of becoming happy or flourishing people. And then in community, people can prosper collectively too. If people are going to prosper collectively, they need some central authority to create rules of the road for them all to know what they have to do in relation to each other. And so in an account of natural law, people need to flourish, people have the end of flourishing, people since they're social creatures should flourish together. But if they're going to flourish together, there needs to be some coordinating mechanism to coordinate how they all flourish. And so law comes to get its justification by being the social instrument that helps people flourish in a community. But that justification sets an end for law too. And that justification creates the elements of Thomas's definition of law. So law has a teleological justification and the end of law is to help people to prosper together in community. And a directive that helps people prosper together all as equal beings is a just law. And that tendency toward justice is what Thomas gets at when he talks about law being an ordinance directed to the common good. But since these ordinances aren't going to work very well, unless people know who can make them and know what they are, the teleological end of the law requires that law be made by somebody in due care, and that they be made in a way that they're promulgated for the benefit of the subjects.