Melvyn Bragg and his guests discuss photosynthesis, the process by which green plants and many other organisms use sunlight to synthesise organic molecules. Photosynthesis arose very early in evolutionary history and has been a crucial driver of life on Earth. In addition to providing most of the food consumed by organisms on the planet, it is also responsible for maintaining atmospheric oxygen levels, and is thus almost certainly the most important chemical process ever discovered.

With:

Nick Lane

Sandra Knapp

John Allen

Producer: Thomas Morris

Melvyn Bragg and his guests discuss the Sino-Japanese War of 1937-45. After several years of rising tension, and the Japanese occupation of Manchuria, full-scale war between Japan and China broke out in the summer of 1937. The Japanese captured many major Chinese ports and cities, but met with fierce resistance, despite internal political divisions on the Chinese side. When the Americans entered the war following the bombing of Pearl Harbor, the Japanese found themselves fighting on several fronts simultaneously, and finally capitulated in August 1945. This notoriously brutal conflict left millions dead and had far-reaching consequences for international relations in Asia.

With:

Rana Mitter

Barak Kushner

Tehyun Ma

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss The Tale of Sinuhe, one of the most celebrated works of ancient Egyptian literature. Written around four thousand years ago, the poem narrates the story of an Egyptian official who is exiled to Syria before returning to his homeland some years later. The number of versions of the poem, which is known from several surviving papyri and inscriptions, suggests that it was seen as an important literary work; although the story is set against a backdrop of real historical events, most scholars believe that the poem is a work of fiction.

With:

Richard Parkinson

Roland Enmarch

Aidan Dodson

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Laurence Sterne's novel Tristram Shandy. Sterne's comic masterpiece is an extravagantly inventive work which was hugely popular when first published in 1759. Its often bawdy humour, and numerous digressions, are combined with bold literary experiment, such as a page printed entirely black to mark the death of one of the novel's characters. Dr Johnson wrote that "Nothing odd will do long. Tristram Shandy did not last" - but two hundred and fifty years after the book's publication, Tristram Shandy remains one of the most influential and widely admired books of the eighteenth century.

With:

Judith Hawley

John Mullan

Mary Newbould

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the Domesday Book, a vast survey of the land and property of much of England and Wales completed in 1086. Twenty years after the Battle of Hastings, William the Conqueror sent officials to most of his new territories to compile a list of land holdings and to gather information about settlements, the people who lived there and even their farm animals. Almost without parallel in European history, the resulting document was of immense importance for many centuries, and remains a central source for medieval historians.

With:

Stephen Baxter

Elisabeth van Houts

David Bates

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Strabo's Geographica. Written almost exactly two thousand years ago by a Greek scholar living in Rome, the Geographica is an ambitious attempt to describe the entire world known to the Romans and Greeks at that time. Strabo seems to have based his book on accounts of distant lands given to him by contemporary travellers and imperial administrators, and on earlier works of scholarship by other Greek writers. One of the earliest systematic works of geography, Strabo's book offers a revealing insight into the state of ancient scholarship, and remained influential for many centuries after the author's death.

With:

Paul Cartledge

Maria Pretzler

Benet Salway

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the science of matter and the states in which it can exist. Most people are familiar with the idea that a substance like water can exist in solid, liquid and gaseous forms. But as much as 99% of the matter in the universe is now believed to exist in a fourth state, plasma. Today scientists recognise a number of other exotic states or phases, such as glasses, gels and liquid crystals - many of them with useful properties that can be exploited.

With:

Andrea Sella

Athene Donald

Justin Wark

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss Max Weber's book the Protestant Ethic and the Spirit of Capitalism. Published in 1905, Weber's essay proposed that Protestantism had been a significant factor in the emergence of capitalism, making an explicit connection between religious ideas and economic systems. Weber suggested that Calvinism, with its emphasis on personal asceticism and the merits of hard work, had created an ethic which had enabled the success of capitalism in Protestant countries. Weber's essay has come in for some criticism since he published the work, but is still seen as one of the seminal texts of twentieth-century sociology.

With:

Peter Ghosh

Sam Whimster

Linda Woodhead

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the work of George Berkeley, an Anglican bishop who was one of the most important philosophers of the eighteenth century. Bishop Berkeley believed that objects only truly exist in the mind of somebody who perceives them - an idea he called immaterialism. His interests and writing ranged widely, from the science of optics to religion and the medicinal benefits of tar water. His work on the nature of perception was a spur to many later thinkers, including David Hume and Immanuel Kant. The clarity of Berkeley's writing, and his ability to pose a profound problem in an easily understood form, has made him one of the most admired early modern thinkers.

With:

Peter Millican

Tom Stoneham

Michela Massimi

Producer: Thomas Morris.

Melvyn Bragg and his guests discuss the Trinity. The idea that God is a single entity, but one known in three distinct forms - Father, Son and Holy Spirit - has been a central belief for most Christians since the earliest years of the religion. The doctrine was often controversial in the early years of the Church, until clarified by the Council of Nicaea in the late 4th century. Later thinkers including St Augustine and Thomas Aquinas recognised that this religious mystery posed profound theological questions, such as whether the three persons of the Trinity always acted together, and whether they were of equal status. The Trinity's influence on Christian thought and practice is considerable, although it is interpreted in different ways by different Christian traditions.

With:

Janet Soskice

Martin Palmer

The Reverend Graham Ward

Producer: Thomas Morris.