One of the reasons people might be fallible, why we might fail to do what we try to do isignorance, that we have a limited understanding of the laws of the world - the physical laws that govern the world and of all the particulars of the world upon which those laws work. And then there's ineptitude, meaning that the knowledge is available, but individuals fail to apply it correctly. The third source is "necessary fallibility." That is, we're never going to be omniscient, there is some knowledge that we will simply never achieve, and there are limits to what we will be able to do.

This is the reality of intensive care: at any point, we are as apt to harm as we are to heal.

Good checklists, on the other hand are precise. They are efficient, to the point, and easy to use even in the most difficult situations. They do not try to spell out everything--a checklist cannot fly a plane. Instead, they provide reminders of only the most critical and important steps--the ones that even the highly skilled professional using them could miss. Good checklists are, above all, practical.

Sometimes we can offer a cure, sometimes only a salve, sometimes not even that. But whatever we can offer, our interventions, and the risks and sacrifices they entail, are justified only if they serve the larger aims of a person's life. When we forget that, the suffering we inflict can be barbaric. When we remember it the good we do can be breathtaking.

Over time I learned that there are two very different satisfactions that you can have in your life. One is the satisfaction of becoming skilled at something. It almost doesn't matter what the terrain is. There is a deep, soul-feeding resonance in mastery itself, whether in teaching, writing a complicated software program, coaching a baseball team, or marshalling a group of people to start a new business.

Developing a skill is painful, though. It is difficult. And that's part of the satisfaction. You will only find meaning in what you struggle with. What you struggle to get good at next may not seem the exact right thing for you at first. With time and effort, however, you will discover new possibilities in yourself-an ability to solve problems, for instance, or to communicate, or to create beauty.

When I do an operation, it's half a dozen people. When it goes beautifully, it's like a symphony, with everybody playing their part.