Professor Murray Gell-Mann is one of the most influential and brilliant scientists of the twentieth century. His work on symmetries, including the invention of the 'quark', in the 1950s and early 1960s has provided a foundation for much of modern particle physics and was recognised by the award of the Nobel Prize for Physics in 1969. This book is a collection of research articles especially written by eminent scientists to celebrate Gell-Mann's 60th birthday, in September 1989. The main body of contributions are concerned with theoretical particle physics and its applications to cosmology.