Both the advice and the warnings are down to earth. Yes, there are risks—ranging from frustration to impalement—but the authors provide good ways to learn to avoid them through your own skill. And scientific or historical tidbits are appended: Did you know that the first batteries were made over 2,000 years ago in Baghdad? It takes work to raise a child who can use a table saw, build a campfire, and chart a course for herself after growing up. But with this book in hand, it'll be a satisfying adventure.

I spoke to Tulley about the impetus for the book, a new school he's opening in San Francisco, and his favorite (dangerous) things.

Why did you write 50 Dangerous Things (You Should Let Your Children Do)?

Every day, new laws are created that further hamper the ways children can engage with the world. As a group we tend to leap to the worst possible conclusions in every scenario.

We see a child climbing a tree and the first thing we think of is how they might fall and be maimed for life, when we might as easily say, "Look at how well Sarah is climbing that tree!" When we protect children from every possible source of danger, we also prevent them from having the kinds of experiences that develop their sense of self-reliance, their ability to assess and mitigate risk, and their sense of accomplishment.

How do you envision the book being used? It seems designed to be kept for years and gradually worked through.

Yes, definitely. Not every topic in the book is immediately accessible or appropriate for every child or family. The idea is that the book is always there, ready to suggest something wonderful and engaging to do. It may be the parent that is not quite ready to do a certain activity, but every time you open the book, you reevaluate yourself and your child. Maybe this time you're ready to let them sit in your lap and drive the car. (That's Dangerous Thing #7.)

You talk about the idea of "competence." Can you explain what you mean by that and how we gain it from tinkering?

We recognize competent people by their behavior when presented with a problem; they tend to assess and then act, formulating a plan and adapting it to the situation as it unfolds. They have a kind of confidence that comes from knowing that things can be figured out, whether they are broken appliances, local water shortages in a remote location, or difficult social situations.

This kind of competence only comes from practice. Persistence and resilience only come from having been given the chance to work though difficult problems. Tinkering is a way of understanding difficult problems, of wrapping our heads around them and quantifying the unknowns.

What kinds of discoveries do kids can make when they're allowed to tinker?

Given the opportunity, kids will build and make things that amaze even themselves. At the Tinkering School camp, we did this project where the kids lashed sticks together—only sticks and string, no nails—to build a big structure, a sort of raised village. And they slept in it.