When I was fifteen years old, I won the egg-drop contest at my high school, the American School in Japan. The goal was to design the smallest, lightest contraption that would protect an egg in a fall from the school’s water tower. My device nested the egg in a cardboard tube attached to a tissue-paper parachute. It would, I hoped, be my first taste of geek stardom.

My physics teacher, Mr. O’Leary, offered a hearty congratulations, and my classmates teased me out of envy. What I remember most, though, was that my victory went unmentioned in the next morning’s public announcements. Our principal regularly played up sports team triumphs and drama club events, so why didn’t a feat of engineering merit acknowledgment? It stung.

That night I thought about why I cared, and the sting gave way to curiosity. I had enjoyed designing the parachute and testing it off my eighth-floor balcony. My egg survived, and I could take pride in that. My self-image as a science whiz was preserved. So what did it matter if others knew? It seemed silly and vain to want more recognition.

I still think of that day as the dawn of my adulthood because I realized then that I was driven by powerful subconscious aspirations: I sought certain kinds of achievement, and I wanted accolades. And while I knew at some level that it was better not to care about public esteem, the aspiration ran deep – I couldn’t reason myself out of it.

The philosopher Peter Singer opens his book The Life You Can Save with one of his favorite thought experiments. Imagine you’re on your way to work when you spot a young child drowning in a pond, but no one is around to save her except for you. Rescuing the child would require you to wade into the water, ruining your new shoes and making you late for work. What do you do? Of course, you would save the child. Weighed against her life, time and cost are nothing.

Singer then asks us to consider a real situation. Every day, thousands of children around the world die of various causes. Many of the deaths could be easily prevented for the price of new shoes. Measles, for example, kills about three hundred people per day, most under the age of five, yet the American Red Cross says that every dollar you donate is enough to vaccinate one child. Most of us could easily afford a dollar a day by cutting back on coffee or choosing a cheaper mobile plan. Some of us could absorb the cost with no change in lifestyle. So why aren’t we saving these dying children?

By juxtaposing the two situations, Singer argues that it’s indefensible that we allow such tragedies. His point is compelling. Innovations for Poverty Action, a nonprofit that Singer endorses, recently received a donation accompanied by a note revealing the inner tension. It read, “Damn you, Peter Singer!” But for every such donor, there are hundreds, if not thousands, who follow the thought experiment and never write a check. When I read about Singer’s drowning girl, my first thought was that I already made annual donations to several causes.Though I agreed with his reasoning, and though I could surely afford to give more, I didn’t reach for my wallet. Why was that?

A slightly different hypothetical gets us closer to the truth: Imagine that you saved one child from drowning a couple of days ago. You promptly bought a new pair of shoes to replace your waterlogged loafers. Then, yesterday, you saw two children in the pond. You saved them both. More shoes. This morning, by some freakish coincidence, there were three drowning children. You saved all of them, too. But that’s a lot of shoes to ruin in a week, and you’ve been late for work three days in a row. You’re worried about tomorrow and the day after. What if, every day, more children needed saving? You doubt you can keep it up.

This is much more like the situation we actually face. Singer cites 27,000 children dying of preventable illness every day, or about 10 million a year. Most of us will happily save one child for a few bucks, but few of us will save all the children we possibly can on an ongoing basis. That would mean a commitment of time and money we’re not ready to make. I’m quite happy to give up 0.1 percent of my annual income, or 1 percent, or 10 percent, or maybe even 20 percent. But 50 percent, 75 percent, or 90 percent?

In other words, the abstract good conflicts with my selfish desires. I give less than I could, consume more than I need, and spend time on activities such as writing this book – which, as much as I hope it serves a positive purpose, is also a bid for self-serving esteem. Even if I put aside guilt, shame, and every other self-admonition, the stark fact is that I’m no saint. I’m unable to be as kind as I know I should be. And that’s the crux. Knowing isn’t enough – I also have to become someone who can better execute what he knows.

Technocrats extol technology and knowledge and intelligence, but positive social change requires a lot more. Millions of people in the world today live satisfying lives envied by the rest. That means that we already have the knowledge we need for well-being. As foreign-aid critic William Easterly wrote, the technocratic illusion is to think that we suffer from a “shortage of expertise.” What we have instead is either a shortage of caring or a shortage of capable follow-through. The question that Singer’s drowning child poses is less about whether to save a child, or even what technology would save the most children. Rather, it’s about how we become the kind of people who can, and will, save more children.

I don’t have easy answers to how we become those people, other than to speculate that it comes through following our deepest aspirations. Despite decades of trying, I’m not sure I’ve grown that much beyond my high-school self. But, one thing I do know is that we have to try. Here in the twenty-first century, we have plenty of amazing technologies. What we need more of are the right kinds of heart, mind, and will.