Being cheerful on the outside can help you – and others – feel it on the inside

Cheerfulness can boost your energy levels, even in tough times - as philosophers and writers have long recognised

The surest sign of wisdom is a constant cheerfulness," wrote the French philosopher Michel de Montaigne in the 16th century. Be cheerful," commands Prospero - arguably the wisest of all of Shakepeare's characters - in The Tempest. Yet the impact of cheerfulness - and the power it gives us to get through difficult moments in our lives - is hard to define and easy to disregard or dismiss, even as we strive to be happy.

And that is one of the reasons Timothy Hampton, a professor in the department of comparative literature at the University of California, Berkeley, decided to write a book about it. Cheerfulness: A Literary and Cultural History explores how cheerfulness" functions as a theme in the works of great philosophers and writers from Shakespeare to Jane Austen, and how it is portrayed in everything from 16th-century medical books to the Boy Scout handbook.