We live in the foreground of experience, though our lives of course have a background too. In the foreground are our immediate preoccupations, our jobs and daily routines, and our families and friends. In the background are all those larger arrangements and broader attachments whose existence we more or less take for granted.

There is a distance, in our lives, between the foreground, which holds our attention, and the background, which engages us only intermittently and without the same degree of personal concern. That this distance should exist is not surprising. Indeed I am inclined to think that it is a condition of ordinary life and psychological well-being.

On Tuesday, the distance between foreground and background disappeared. We were all confronted, in an instant and in the most immediate way, with questions we rarely ask because they belong to the background of our lives, a background whose benign continuity allows us to concentrate our energies on the questions that have urgency and importance for us as individuals.

I go to the ATM to get cash to buy groceries for dinner. But I never think about the web of connections, electronic and otherwise, on which every transaction of my daily life depends. After Tuesday, I cannot get these connections out of my mind. Every button I press, every call I make, reminds me that the life I live is possible only in a sprawling commercial civilization, whose own existence depends on a vast network of connections every one of which now appears as a potential point of vulnerability.

How can this network, and the material existence it sustains, be preserved without exposing us all to dangers that are amplified by the network itself?

I go to the airport and fly across the country. I drive across town. And I express my views without fear they will land me in jail or subject me to the torturer’s prod. These things too, like my withdrawal from the cash machine, depend upon a system of background institutions, of freedoms and courts to enforce them, and upon a culture of tolerance and respect. But I don’t think about this background much, though I depend on it completely.

After Tuesday, there has not been a moment when I haven’t been thinking about these freedoms and this culture, which are virtues but vulnerabilities too, and whose preservation, to which I am committed with all my heart, now poses larger questions than at any time in my life.

I vote in elections and spend time talking about politics with my friends. And when I do, I naturally think about what it means for me to be an American, and I feel an attachment to my country. But these thoughts are only occasional, and this attachment is vague and undefined. Most of my thoughts and feelings concern matters much closer to home. Being an American is, for me, part of the background of life.

But Tuesday put it in the foreground, for me and millions of others. Witness to the suffering, and to the monumental outpouring of support it has provoked, I feel my American identity more vividly than ever before. But what am I now called upon to do as an American? How can I help protect the country I love from those who would destroy it, while protecting all the things that make it worth loving? That is a question, too, that belongs to the background of life but that has now been thrust into the foreground and placed at center stage.

I suspect that it may be a long time before the distance between foreground and background re-establishes itself, though in the end it will and must. But in the meantime we find ourselves confronted with questions that are both rare and deep, and for which — if we are to answer them responsibly — we must summon all our individual and collective resources of mind and heart.

Anthony T. Kronman is dean of the Yale Law School and Edward J. Phelps professor of law.