Melvyn Bragg and guests discuss one of Plato's most striking dialogues, in which he addresses the real nature of power and freedom, and the relationship between pleasure and true self-interest. As he tests these ideas, Plato creates powerful speeches, notably from Callicles who claims that laws of nature trump man-made laws, that might is right, and that rules are made by weak people to constrain the strong in defiance of what is natural and proper. Gorgias is arguably the most personal of all of Plato's dialogues, with its hints of a simmering fury at the system in Athens that put his mentor Socrates to death, and where rhetoric held too much sway over people. WithAngie Hobbs Professor of the Public Understanding of Philosophy at the University of SheffieldFrisbee Sheffield University Lecturer in Classics and Fellow of Downing College, University of CambridgeAndFiona Leigh Associate Professor in the Department of Philosophy at University College LondonProducer: Simon Tillotson

Melvyn Bragg and guests discuss the British phase of a movement that spread across Europe in the mid-19th and early 20th centuries. Influenced by Charles Baudelaire and by Walter Pater, these Decadents rejected the mainstream Victorian view that art needed a moral purpose, and valued instead the intense sensations art provoked, celebrating art for art’s sake. Oscar Wilde was at its heart, Aubrey Beardsley adorned it with his illustrations and they, with others, provoked moral panic with their supposed degeneracy. After burning brightly, the movement soon lost its energy in Britain yet it has proved influential.The illustration above, by Beardsley, is from the cover of the first edition of The Yellow Book in April 1894.WithNeil Sammells Professor of English and Irish Literature and Deputy Vice Chancellor at Bath Spa UniversityKate Hext Senior Lecturer in English Literature at the University of ExeterAndAlex Murray Senior Lecturer in English at Queen’s University, BelfastProducer: Simon Tillotson

Melvyn Bragg and guests discuss William Herschel (1738 – 1822) and his sister Caroline Herschel (1750 – 1848) who were born in Hanover and made their reputation in Britain. William was one of the most eminent astronomers in British history. Although he started life as a musician, as a young man he became interested in studying the night sky. With an extraordinary talent, he constructed telescopes that were able to see further and more clearly than any others at the time. He is most celebrated today for discovering the planet Uranus and detecting what came to be known as infrared radiation. Caroline also became a distinguished astronomer, discovering several comets and collaborating with her brother.WithMonica Grady Professor of Planetary and Space Sciences at the Open UniversityCarolin Crawford Institute of Astronomy, Cambridge and an Emeritus Fellow of Emmanuel College, University of CambridgeAndJim Bennett Keeper Emeritus at the Science Museum in London.Studio producer: John Goudie

Melvyn Bragg and guests discuss an early masterpiece of French epic poetry, from the 12th Century. It is a reimagining of Charlemagne’s wars in Spain in the 8th Century in which Roland, his most valiant knight, chooses death before dishonour, guarding the army’s rear from a pagan ambush as it heads back through the Roncesvalles Pass in the Pyrenees. If he wanted to, Roland could blow on his oliphant, his elephant tusk horn, to summon help by calling back Charlemagne's army, but according to his values that would bring shame both on him and on France, and he would rather keep killing pagans until he is the last man standing and the last to die.The image above is taken from an illustration of Charlemagne finding Roland after the Battle of Roncevaux/Roncesvalles, from 'Les Grandes Chroniques de France', c.1460 by Jean Fouquet, Bibliotheque Nationale, Paris, Ms Fr 6465 f.113 With Laura Ashe Professor of English Literature and Fellow in English at Worcester College, University of OxfordMiranda Griffin Assistant Professor of Medieval French at the University of Cambridge and Fellow of Murray Edwards CollegeAndLuke Sunderland Professor in the School of Modern Languages and Cultures at Durham UniversityStudio producer: John Goudie

Melvyn Bragg and guests discuss the simple animals which informed Charles Darwin's first book, The Structure and Distribution of Coral Reefs, published in 1842. From corals, Darwin concluded that the Earth changed very slowly and was not fashioned by God. Now coral reefs, which some liken to undersea rainforests, are threatened by human activity, including fishing, pollution and climate change. WithSteve Jones Senior Research Fellow in Genetics at University College LondonNicola Foster Lecturer in Marine Biology at the University of Plymouth AndGareth Williams Associate Professor in Marine Biology at Bangor University School of Ocean SciencesProducer Simon Tilllotson.

Melvyn Bragg and guests discuss the author and philosopher Iris Murdoch (1919 - 1999). In her lifetime she was most celebrated for her novels such as The Bell and The Black Prince, but these are now sharing the spotlight with her philosophy. Responding to the horrors of the Second World War, she argued that morality was not subjective or a matter of taste, as many of her contemporaries held, but was objective, and good was a fact we could recognize. To tell good from bad, though, we would need to see the world as it really is, not as we want to see it, and her novels are full of characters who are not yet enlightened enough to do that.WithAnil Gomes Fellow and Tutor in Philosophy at Trinity College, University of OxfordAnne Rowe Visiting Professor at the University of Chichester and Emeritus Research Fellow with the Iris Murdoch Archive Project at Kingston UniversityAndMiles Leeson Director of the Iris Murdoch Research Centre and Reader in English Literature at the University of ChichesterProducer: Simon Tillotson

Melvyn Bragg and guests discuss the republic that emerged from the union of the Kingdom of Poland and Grand Duchy of Lithuania in the 14th Century. At first this was a personal union, similar to that of James I and VI in Britain, but this was formalised in 1569 into a vast republic, stretching from the Baltic to the Black Sea. Kings and princes from across Europe would compete for parliament to elect them King and Grand Duke, and the greatest power lay with the parliaments. When the system worked well, the Commonwealth was a powerhouse, and it was their leader Jan Sobieski who relieved the siege of Vienna in 1683, defeating the Ottomans. Its neighbours exploited its parliament's need for unanimity, though, and this contributed to its downfall. Austria, Russia and Prussia divided its territory between them from 1772, before the new, smaller states only emerged in the 20th Century. The image above is Jan III Sobieski (1629-1696), King of Poland and Grand Duke of Lithuania, at the Battle of Vienna 1683, by Marcello Bacciarelli (1731-1818)With Robert Frost The Burnett Fletcher Chair of History at the University of AberdeenKatarzyna Kosior Lecturer in Early Modern History at Northumbria UniversityAndNorman Davies Professor Emeritus in History and Honorary Fellow of St Antony’s College, University of OxfordProducer: Simon Tillotson

Melvyn Bragg and guests discuss the race to build an atom bomb in the USA during World War Two. Before the war, scientists in Germany had discovered the potential of nuclear fission and scientists in Britain soon argued that this could be used to make an atom bomb, against which there could be no defence other than to own one. The fear among the Allies was that, with its head start, Germany might develop the bomb first and, unmatched, use it on its enemies. The USA took up the challenge in a huge engineering project led by General Groves and Robert Oppenheimer and, once the first bomb had been exploded at Los Alamos in July 1945, it appeared inevitable that the next ones would be used against Japan with devastating results.The image above is of Robert Oppenheimer and General Groves examining the remains of one the bases of the steel test tower, at the atomic bomb Trinity Test site, in September 1945.WithBruce Cameron Reed The Charles A. Dana Professor of Physics Emeritus at Alma College, MichiganCynthia Kelly Founder and President of the Atomic Heritage FoundationAndFrank Close Emeritus Professor of Theoretical Physics at the University of Oxford and a Fellow of Exeter College, OxfordProducer: Simon Tillotson

Melvyn Bragg and guests discuss Anne Bronte's second novel, published in 1848, which is now celebrated alongside those of her sisters but which Charlotte Bronte tried to suppress as a 'mistake'. It examines the life of Helen, who has escaped her abusive husband Arthur Huntingdon with their son to live at Wildfell Hall as a widow under the alias 'Mrs Graham', and it exposes the men in her husband's circle who gave her no choice but to flee. Early critics attacked the novel as coarse, as misrepresenting male behaviour, and as something no woman or girl should ever read; soon after Anne's death, Charlotte suggested the publisher should lose it for good. In recent decades, though, its reputation has climbed and it now sits with Jane Eyre and Wuthering Heights as one of the great novels by the Bronte sisters.The image above shows Tara Fitzgerald as Helen Graham in a 1996 BBC adaptation.WithAlexandra Lewis Lecturer in English and Creative Writing at the University of Newcastle (Australia)Marianne Thormählen Professor Emerita in English Studies, Lund UniversityAndJohn Bowen Professor of Nineteenth Century Literature at the University of YorkProducer: Simon Tillotson

Melvyn Bragg and guests discuss the Greek writer known as the father of histories, dubbed by his detractors as the father of lies. Herodotus (c484 to 425 BC or later) was raised in Halicarnassus in modern Turkey when it was part of the Persian empire and, in the years after the Persian Wars, set about an inquiry into the deep background to those wars. He also aimed to preserve what he called the great and marvellous deeds of Greeks and non-Greeks, seeking out the best evidence for past events and presenting the range of evidence for readers to assess. Plutarch was to criticise Herodotus for using this to promote the least flattering accounts of his fellow Greeks, hence the 'father of lies', but the depth and breadth of his Histories have secured his reputation from his lifetime down to the present day.WithTom Harrison Professor of Ancient History at the University of St AndrewsEsther Eidinow Professor of Ancient History at the University of BristolAndPaul Cartledge A. G. Leventis Senior Research Fellow at Clare College, University of CambridgeProducer: Simon Tillotson