The past is unfashionable right now: cutting ourselves off from our roots, drawing a line under things, modernising, reinventing - that's what we like doing. That old stuff, tradition and so forth, it's a bit passe now, isn't it?

Living Ideas, this week's Postscript series on Radio 3, was based on the positively nerdy belief that history isn't so easily got rid of; you think you've wiped it off your shoes, but the smell clings. Four contemporary thinkers argued the relevance of their predecessors to the world we live in, starting with the American philosopher Martha Nussbaum, who put the case for "Stoic cosmopolitanism".

Cosmopolitanism was invented by Diogenes the Cynic - a man famous for 2,000 years for living in a barrel - which wouldn't get him more than 15 seconds of air time in the Ten O'Clock News "And finally ..." slot if he were alive today. The Stoics only popularised it. A cosmopolitan is, literally, a "citizen of the world". Cosmopolitanism held that class, rank, status, national origin and gender are irrelevant to moral worth; we may have local ties and preferences, but we are all part of a common human community. You can see the aspiration at work in modern phenomena from the International Court at the Hague to the Bill and Ted films, with their powerful moral, "Be cool to one another".

But the irrelevance of class and rank remains an ideal, and possibly not even that, in a country where placating the rich has become one of the first principles of government. Machiavelli's practical political thought, the subject of Quentin Skinner's slot on Wednesday, seems to have had more concrete influence. The good ruler, quoted Skinner, knows how to vary his conduct with the winds of fortune, and knows that appearance is everything. Is there some modern politician Skinner could have had in mind? Come to that, are there any Skinner could not have had in mind?

The power of history to shape the present was given its full due in Empire (Radio 4, Monday), where Peter Jay took Gibbon's Decline and Fall of the Roman Empire as the model for a four-part obituary of the British Empire. The first programme was dragged down by a cliched production - an imperial march by William Walton, clopping hooves, cheering crowds - and by Jay's over-assured delivery. But underneath lay an appealing intellectual shyness, an unwillingness to put forward explanations and motives for such a loose, heterogeneous phenomenon, as Jay moved towards the reflection that what can happen, will happen.

Fortunately, that isn't true, as evidenced by Kennedy's Secret Tapes (Radio 4, Wednesday), an account of the Cuban missile crisis of 1962. Anthony Howard, all breathless intelligence, narrated and Ed Bishop made a strangely sheepish JFK. What could have happened here was a nuclear strike on Cuba - in fact, the programme suggested, it came closer to happening than people realised at the time. Listening, you felt a trickle of uneasy relief that it didn't; and realised that this is what really matters about history: it's still going on.