What is the meaning of life? I once wrote to every philosopher in the UK to ask them. Their answers were meagre and dispiriting. One even included a death threat.

Since then I've moved on study why babies have such a great time being babies. Anyone who has met a baby knows how much they delight in the world. As a baby scientist I set out to discover why babies laugh so much more than the rest of us and what it tells us about the human condition. I've written a whole book about this but to save you reading it I will summarise the secret of babies happiness and reveal how it fits in nicely with the best answers to the meaning of life.

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