Because we imagine, we can have invention and technology. It's actually play, not necessity, that is the mother of invention.

Some people say that parents don't matter, and that's not true at all. The irony is that we pay attention to all these things that don't matter, and not to what does matter, such as parents having enough resources to provide an environment where their children have both security and freedom.

Teaching is a very effective way to get children to learn something specific - this tube squeaks, say, or a squish then a press then a pull causes the music to play. But it also makes children less likely to discover unexpected information and to draw unexpected conclusions.

From an evolutionary perspective children are, literally, designed to learn. Childhood is a special period of protected immaturity. It gives the young breathing time to master the things they will need to know in order to survive as adults.

All of us gardeners know that nothing comes out the way you planned. It's a different garden every year, and it's always sort of different from what you were thinking when you began. What it really means to be a good gardener is to work hard to produce an ecosystem that will have enough diversity, enough possibilities, so it's robust, and it's resilient, and it can change when the seasons change. And that kind of robust, unexpected, variable, messy system - that's what you want to create when you're having children, too.

Philosophers and psychologists have long puzzled over the question of how we know as much as we do despite our limited experiences. One way is to see how children learn. Another example is consciousness. The concept is usually explored by armchair academics. Looking at kids expands our conceptions of consciousness.

Developmental scientists like me explore the basic science of learning by designing controlled experiments.