In an explanation of St. Thomas Aquinas’s Treatise on Law, you say that the purpose of the common good “belongs” to the whole people. Could you tell me how a purpose "belongs" to someone? Any light you can shed on this would be very much appreciated.
I don’t mean anything terribly abstruse. A purpose belongs to me if it’s my purpose, belongs to you if it’s your purpose, and belongs to the community if it’s the community’s purpose. Terms like “my” can be puzzling because they are used in different senses. For example, if I speak of “my” car, I mean that I own it, but if I speak of “my” wife, I mean that I am the person who is related to her as husband to wife.
How then is a purpose mine? It’s mine when I am interiorly ordered or directed to it. Ordered or directed to it how? Well, it may be my subjective intention (for example, I may want to get some ice cream), it may be my inbuilt or natural purpose (for example, even if I want to die, I am naturally directed to life and flourishing), or it may be both (I am naturally directed to life and flourishing, but I subjectively aim at a flourishing life too).
We’re also speaking in both senses when we say that the purpose of the common good “belongs” to the political community. Certainly the community cannot be said to flourish unless it really is enjoying the common good; as Aristotle says in Politics, Book 1, the city “comes into existence for mere life -- but exists for the sake of living well.” So the purpose of the common good is natural to it. But unless the common good is the city’s subjective intention too, it is hardly proper to call the city a “community.” The very phrase calls attention to what it cherishes and pursues in common. I hope I’ve cleared up the puzzle!