Everything has been figured out, except how to live. – Jean Paul Sartre
One of the great difficulties with prudence is that it presumes a basis for knowledge. Aristotle and Plato found this basis through metaphysics, especially Plato's concept of unchanging eternal forms. Greek philosophy feels alien to most people in the twenty-first century.
Similarly, Christian theology offers no definitive answer as to why God created humans. Catechistical answers such as to "glorify God" anthropomorphize God, attributing human feelings and motives to the divine. In fact, the Bible does not answer the question of why; the book of Job, which contains a long soliloquy in which Job beseeches God about the meaning of things, ends with God replying that God, not Job, is God (a most frustrating answer!).
Thankfully, Sartre was wrong. Twentieth century American philosopher John Rawls offers an alternative. He defined prudence (or practical reason) in terms of what is contextually reasonable, decent, or rational, deriving those three principles from his concept of justice as fairness:
… at no point are we deducing the principles of right and justice, or decency, or the principles of rationality, from a conception of practical reason in the background. Rather, we are giving content to an idea of practical reason and three of its component parts, the ideas of reasonableness, decency, and rationality. The criteria for these three normative ideas are not deduced, but enumerated and characterized in each case. Practical reason as such is simply reasoning about what to do, or reasoning about what institutions and policies are reasonable, decent, or rational, and why. There is no list of necessary and sufficient conditions for each of these three ideas, and differences of opinion are to be expected. We do conjecture, however, that, if the content of reasonableness, decency, and rationality is laid out properly, the resulting principles and standards of right and justice will hang together and will be affirmed by us on due reflection. (The Law of Peoples (Cambridge, MA: Harvard University Press, 1999), p. 87)
Reasonable citizens "… are characterized by their willingness to offer fair terms of social cooperation among equals and by their recognition of the burdens of judgment." (The Law of Peoples, p. 87)
Rawls describes a decent society as one that
… is not aggressive and engages in war only in self-defense. It has a common good idea of justice that assigns human rights to all its members; its basic structure includes a decent consultation hierarchy that protects these and other rights and ensures that all groups in society are decently represented by elected bodies in the system of consultation. Finally, there must be a sincere and not unreasonable belief on the part of judges and officials who administer the legal system that the law is indeed guided by a common good idea of justice. Laws supported merely by force are grounds for rebellion and resistance. They are routine in a slave society, but cannot belong to a decent one. (The Law of Peoples, p. 88)
Rational societies are communities who determine their choices using counting principles, e.g., through voting or cost-benefit analyses (The Law of Peoples, p. 88).
Prudence, Rawls also argued, is contextual. People exercising prudential wisdom will frequently disagree over important, substantive issues, e.g., tax policy and theology. Michael Novak helpfully reminds us, "Universal principles need not be univocal." (The Universal Hunger for Human Liberty (New York: Basic Books, 2004), p. 228)
Rawls' identification of prudence with contextually appropriate choices by reasonable, decent, and rational communities addresses the basic Christian question of how should we live in the present. Shifting the focus from the individual to the community reduces the probability of an individual substituting pride for prudence, as Garfield's physician did. Of course, a community may become demonic, as occurred in post-WWI Germany when a defeated, discouraged nation aided the Nazis in their ascent to power.
The person of faith rightly turns to their faith community as the community of reference for determining prudence. For this reason (along with others!), we do well to avoid fundamentalism and other doctrinaire communities that are not reasonable, decent, and rational. The Westboro, KA, Baptist Church exemplifies this abhorrent type of community that profanes the name of Christianity with its unreasonable (God only loves some people), indecent (protesting at funerals of veterans), and irrational (these protests will prompt people to repent) acts. In contrast, healthy faith communities are reasonable (God created minds for people to use), decent (God calls us to love one another because God created all with dignity and worth), and rational (we weigh perceived pros and cons of alternatives then choose what appears to be best, confident that this is how God leads us).