I am in debt of an explanation: why did I say that Justice Marshall's reading of the Massachusset's constitution doesn't fall under the label of juris prudentia?
The simplest explanation, true but too short, it is that she is ignorant: there can't be no prudence without learning.
On the other side, I could bore you with learned explanations of what was prudentia, in Latin, or phronesis, in Greek. But I'll spare you.
I'll ask: what's the use of learning, I mean, wide ranged erudition?
The answer is simple: to learn how to play.
Can you imagine a musician knowing just one score? And playing always that?
Simplifying, the beauty of music comes from the combination of seven notes, and all the variations and tranformations to which it lends itself. Just knowing the notes and the rules of their combination is not enough to become a musician. You must have learned many scores to know how to play.
Still, simple musical erudition is not enough. Exspecially if you need to be able to improvise, as in the jam sessions typical of American jazz. You need an extra factor, a sensibility for music, which can be cultivated but not taught by training in the rules underlying the scores.
You need musical intgelligence, to be music-wise, or, if I may say so, music-prudent.
I have no idea of Justice Marshall's legal erudition. But the sentence to which she gave her words sounded like coming from nowhere, just based on a definition of the elements of society and the law to rule their interaction. No precedents, no backgraound of variantions on the themes of social life. Of life, period.
After all, what else is required save to obey to the rules which the state makes, by way of legislators, or of judges taking their place if they think them too prone to grant people an intelligent understanding of what they want?
Who needs music, who needs all the stories of old which used to teach how to play life?
Who needs prudence?