My beloved Caleb,

When you were six months old, I thought you were about as terrific as any child could be and found myself wishing you could stay that age forever. I was resigned to the fact that as you grew older, you would inevitably become a little less appealing and a little more aggravating.

But it hasn't worked out that way. Even though you're a big boy now -- six years old -- you're still the most terrific child I know. Oh, sure, you can be exasperating at times: Mama and I were ready to tear our hair out, for example, when for seven straight weeks of swimming lessons last summer, you refused to even get in the water. Like every child, you occasionally misbehave, or speak disrespectfully, or throw a minor fit when you don't get your way. But on the whole, you're a joy to be with -- cheerful, bright, enthusiastic.

And funny, too. You told me a few months ago that you plan to live in our house even after you get married. "Where will you sleep?" I asked. "In my room," you answered. "And where will your wife sleep?" "In the top bunk."

These days, Caleb, I often marvel at how grown you seem. The chubby toddler I remember has given way to a lean young fellow with a competitive streak and a mind of his own. When I took you and Mama to the airport in February for your trip to Disneyworld with Grandma Weller, I watched you stride into the terminal, suitcase in hand, and was struck by what a seasoned little traveler you'd become.

Yet in other ways, you're still so innocent: When you packed that suitcase for the trip to Florida, the first thing that went in was your favorite stuffed animal -- Peter Rabbit.

I'm in no hurry to dispel your innocence, but I know that the world outside won't stay outside forever. My power to shelter you from the worst of what's out there is gradually decreasing; your awareness of human evil and suffering are slowly on the rise. I want to prepare you for the ugliness and injustice that you are bound to encounter as you make your way in the world -- prepare you not just to recognize that such things exist but to understand that you have a duty to combat them.

We talked about the war in Iraq the other day. I explained to you that the ruler of that country is an extremely cruel man who for a very long time has been killing and hurting many people -- including even children your age and younger -- and that the United States was now leading a war to stop him. War can be very terrible and frightening, I told you, but it would be more terrible and frightening if we did nothing to stop the cruel man.

"Imagine how you would feel," I suggested, "if somebody were hurting you very badly -- hurting you so badly that you were crying -- and everyone else just watched and did nothing to stop him." That is a very simple way to frame the case for war in Iraq, Caleb, but you'd be surprised how many adults cannot seem to grasp it.

Fortunately, the idea that the persecution of innocents demands a response is one with which you are already familiar.

In kindergarten right now, you and your classmates are preparing for Passover. You are learning about the bitter enslavement of the Israelites and the cruelty of the Egyptians, and about the great leader named Moses, who refused to look the other way when he came across acts of injustice. Once again you are hearing the story of Shifra and Puah, the Hebrew midwives who bravely defied Pharaoh's command to drown every newborn Hebrew boy.

The lesson I hope you are gradually internalizing is that when victims are suffering, those who can rescue them have an obligation to do so. "Do not stand aloof from the blood of your neighbor," commands the Bible in Leviticus 19:16. When someone is in a desperate predicament, you must help if you can. And sometimes the only way to help is through fighting and bloodshed. Awful as war is, the alternative can be even worse.

The truth is, Caleb, if it weren't for war, you would not exist. In the spring of 1945, your father's father was near death in a Nazi concentration camp; he survived and was liberated thanks to the bombs and bullets of the Allies, who managed to destroy Hitler before Hitler managed to destroy every last Jew in Europe. Men with guns saved your family from extinction. Never forget that.

In a few days we'll be sitting down to the Passover seder, and I look forward to hearing you explain the meaning of the ancient rituals. We eat bitter herbs, you'll tell me, to recall the bitter bondage of our ancestors. We dip a vegetable in salt water to remind ourselves of their tears. We eat dry, unleavened matza, because it was the bread of their affliction.

We live today in freedom and comfort, but there are so many in this world who know only bondage and tears. Don't close your eyes and ears to them, Caleb. Train yourself to care about those who are being hurt. And never forget: Evil men triumph when good men do nothing.