By Joseph Wood.

Aristotle has given much to the Catholic understanding of "what is," of reality. Among his gifts were three axioms about man:

• All men naturally desire knowledge.

• All men are by nature rational and political animals.

• All men want to be happy, and by nature are supposed to be happy.

We are, by the given order of nature, beings who want to know, do, and be something. Those desires form our human nature. They are closely related, and when one desire is frustrated, there are consequences for the other desires and for our capacity to be fully human.

Aristotle claimed that in wanting to be happy, we are really meant to use our reason and intellectual excellence to contemplate the divine. We want the wisdom of knowing the causes and truths of the highest, metaphysical things, which don't change and exist beyond the naturally changing world we sense.

But he concludes, we can't live our telos, or our proper end of knowing the divine things, the fullness of our human nature - mainly because we are occupied with taking care of the needs of our bodies. We're composites of body and soul, always animals yet always with a uniquely human capacity for reason.

Yet no need for despair. Aristotle advises us that we can have good lives in politics. We can cultivate human excellence in political communities, which come to exist by nature to know the common good of the community and to do it.

So the knowing and doing of being human are closely linked. That linkage shows up in other philosophical thought as well.

Aristotle's teacher, Plato, in his dialogues Republic, Gorgias, and Statesman, shows Socrates (or a stand-in) using reason to discuss justice and governance in political communities. In the Republic, Plato devotes time not just to politics but to how we know truth, through reason, in his famous "divided line" explanation of the range of human understanding and the allegory of the cave.

But in these dialogues, wisdom or knowing the "what is" of politics requires that the philosopher turn to myths involving the nature and action of the divine as sources of truth. Socrates warns that his opponents will think of these myths just as old wives' tales, but we should take what they offer until a more reliable source of truth is found.

Modern political philosophers such as Thomas Hobbes and John Locke also ground their political thought on their own epistemological theories. In both cases, our understanding of what is outside of us is very limited, so interior reason (rather than nature or God) becomes the dominant source of truth.

We can expect, then, that when we are frustrated in our knowledge, we are frustrated in our politics. Our knowing the truth of the genuine common good precedes the political choices of doing that good.

In his book The Discarded Image, C.S. Lewis surveys medieval literature in order to discern the model by which medieval man viewed the world, which shaped how he knew what he knew. That model was less empirical or "evidence based" than the modern "paradigm." It encouraged a vertical outlook - towards the heavens, the divine, and was open to truths that could not be empirically certified but could be known through a broader reason.

Our modern horizontal view, already dominant by the 17th or 18th centuries, tends to be restricted to the findings of physical science, discarding the contemplation of the divine that Aristotle thought to be the fullness of human nature. It has produced enormous material progress based on industrial and now digital methods. But it leaves out much of reality, as Pope Benedict XVI brilliantly pointed out.

Many people have felt uneasy about this modern way of knowing. Father Paissy in Dostoevsky's Brothers Karamazov captures this distrust:

The science of this world, having united itself into a great force, has. . .examined everything heavenly that has been bequeathed to us in sacred books, and after hard analysis, the learned ones of this world have absolutely nothing left of ...