It can be hard to get my almost-four-year-old son to answer a direct question—like “What happened at school today?” or “Why is your brother crying?” or “How did all this water end up on the floor?”—but when he is in the mood to share, he is full of information. His confident pronouncements are a window into his preschool mind, one I’m glad to have. They make me smile. But they can also make me sweat. Riding in the car or sitting down to lunch, he’ll try out a new word or explain a concept he thinks he understands, and I am suddenly on the spot: This is it, Mommy, a chance to set the kid straight or send him down the wrong road. Don’t blow it.

So, if he announces, as he did the other day, “‘Frustrated’ is when you can’t reach something,” I figure I owe him at least a hint at the broader meaning of frustration. I want him to be confident, but also correct. Still, I have to tread lightly; if I make him feel foolish for speaking up, or just bore him to tears with my answer (“Well, actually…”), he may stop volunteering these little insights, and then I’ll know even less about what’s going on in his head.

It’s exhausting enough staying on my toes when the stakes are low—I know he’ll get his vocabulary straight eventually. But sometimes crucial character-building moments catch me unprepared. I certainly wasn’t ready for the day he declared, “Mommy, ‘poor’ is the same thing as ‘sad.’”

We had just been reading a storybook about “an old man and his wife” who “were very poor.” So I knew where he was coming from. What I didn’t know was how I should respond. Quick, I thought, say something wise and simple and profound, something a really good parent would say, something that will set him on the road to a life of virtue, before he changes the subject back to what various kinds of dinosaurs ate.

Don’t say too much. Don’t say too little. Give him a nudge in the direction of compassion without pushing him over into anxiety. While all this went on in my head, he was looking expectantly at me. So I tried to explain, in simple terms, what poverty is, and that being poor can make people sad. I think I went on to tell him that the opposite of “poor” is “rich,” and that people who have more than enough should help people who have too little. All the while I was checking my tone: not too flip, not condescending, not ponderous. I didn’t want to tip him off at the age of not-quite-four to the heavy reality of poverty as a social issue, far more complicated than a folktale, and much harder to set right. I don’t want him to think that poverty can be fixed, or papered over, just by cheering people up. I don’t want to give the impression that happiness comes from having a lot of stuff (especially with his birthday coming up). And I wanted to avoid sounding like the charity worker in the Danny Boyle film Millions who asks a group of schoolchildren, “Who feels sorry for poor people?” and then, when they all raise their hands, says approvingly, “Correct answer!”

I got through it. The moment passed. But did he take anything away from that conversation, and if he did, was it the right thing? Does he have a deeper understanding of what it means to be “poor,” even in a story, if not yet in the real world? Or did he walk away thinking, “Better not bring up poor people and/or sadness again, because it sure makes Mommy nervous?”

I suppose I should try to relax and enjoy these moments when my kids are still exploring the world out loud. It won’t be long before adolescence looms and they start keeping their insights and questions to themselves, leaving me wondering what’s troubling them and how I can help make it right. (Frustration, they say, is when you can’t reach something.) There is something delightful about having the chance to examine a familiar word or concept with new eyes. And nothing gives a rusty brain on maternity leave a workout like trying to define grown-up concepts (weather forecasting, patriotic holidays, religious doctrine) in terms a toddler can understand.

Maybe I don’t need to have all the answers. “What does ‘Immaculate Conception’ mean?” he wanted to know this morning. Sometimes I think it’s best for all of us if I just say, “Hey, how about those meat-eating dinosaurs?”