FLORENCE – A tourist in Florentine museums is like a skipping stone above unfathomable depths.

Here a Botticelli. There a Donatello. A single room at the Uffizi that would reward a lifetime of study gets five hurried minutes before lunch.

I have no intention of performing art criticism without a license (a capital offense here in Italy). But a few things stand out even to the amateur eye.

The medieval rooms display art for the sake of God. The artists reveal all the glories that two dimensions have to offer. But they are often anonymous. And their subjects – even Jesus on the cross – usually have the kind of flat, calm faces associated with Byzantine art. In a universe structured and ordered by the divine, piety is expressed by serenity.

In the Renaissance rooms, it is art for the sake of humanity. The subjects, liberated from flatland, walk into the room. The artists – sometimes celebrities in their own right – mine Classical and Christian stories for drama, sex and violence. Their statues and paintings are intended to express the best of human craft, endeavor and ambition. In this sense, they produced a very public, even civic, art.

By the time you reach the face of Michelangelo’s David, it is supremely confident, prepared and determined. Previous artistic Davids were usually depicted as scrawny youths, which emphasized God’s miracle of deliverance in the fight against Goliath. This David is no longer in need of miracles. Other than the sling on his back, he has nothing to do with the biblical story and everything to do with a spirit of humanism, optimism and pride. Originally intended to adorn a church, David was placed in the town square as a symbol of Florence’s public virtues.

And then you reach the Caravaggio room at the Uffizi, and you know you are seeing something entirely different. The face of the Medusa cries out with inner agony. The artist – accused of murder, fleeing from place to place – is working out his own demons in the form of art. He is exploring the wild, disordered landscape of his own psyche – the inner human geography that Freud will eventually describe in detail.

Then – your eyes adjusting to the vivid December sunlight – you return to an Italian street. It is pleasant enough. (I would take modernity plus advanced medicine and dentistry over the Renaissance plus the Black Plague.) But in the world around you, the most visited monuments seem to be, not churches or galleries, but high-end boutiques. Most Western societies, including the United States, have reached the stage of secularism without humanism. Our greatest efforts are spent on getting and keeping. Our defining creed is consumerism. Our memorials, according to T.S. Eliot, will be “the asphalt road and a thousand lost golf balls.”

That isn’t entirely fair, but it feels true. In response, I might be expected to urge a return to option No. 1 – a medieval God intoxication. But that isn’t even a choice. Individuals still believe in God, of course. But the medieval world-view found God in every choice and hour of the day – in every celestial movement and every terrestrial event. That social consensus is unrecoverable.

And, God knows, we have enough of option No. 3 – an individualism focused on self-judgment, self-expression, self-improvement and self-actualization.

Our best hope, I suspect, is option No. 2. What we need is a revival of humanism. This need not be secular humanism (though it will be for some). In the Renaissance, humanism involved claiming every area of achievement in art or science for human excellence and civic pride. It was displayed in the relentless emphasis on decoration. Every clock, every chair, every gun handle, every scientific instrument, every bit of door, or floor, or ceiling was stamped with human creativity and given lasting worth. It was a declaration against time and decay that the world is not disposable. That humans could leave a lasting mark.

The Renaissance was the finest kind of revolution – oriented toward the future, but rooted in the best of the past. The rediscovery of the classical world sparked and fueled something entirely new. This balance of conservative and liberal is the best driver of social dynamism. It is the type of restless, rooted ambition that also characterized America’s founding and inspired our best civic achievements, from the Library of Congress to “Leaves of Grass” to the moon shot. These are either sources of inspiration, or mere nostalgia.

Michael Gerson is a columnist for The Washington Post. Reach him via e-mail at michaelgerson@washpost.com.