You can see where Kellner got the idea - socialism didn't work, nobody's found a cure for cancer, and ooh, you see some terrible things on the news - but this theorising surely had more to do with pre-millennial tension than with the failure of the Philosophes. For one thing, rationalism has never had quite the thorough-going social impact that Kellner claimed. And in any case, the version of the Enlightenment which he was poking holes in, one that offered scientific certainty but denied fundamental moral truths, isn't one you meet very often. Most Enlightenment thinkers would hold at least some truths to be self-evident; most scientists would say that they offer plausible hypotheses rather than certainty.
Where Kellner was on the right lines was in suggesting that we could turn to a modified rationality, one that takes uncertainty into account. In fact, this is the rationality that most of us already cling to: we call it "common sense".
Common sense was also enthroned by Irma Kurtz in The Lying Game (R4, Wednesday), a two-part exploration of untruth. It's common sense, according to Kurtz, which tells us that lying is wrong. Sadly, common sense is apparently at odds with 16-million-year-old instinct here. The ability to deceive is something that all primates have inherited from a common ancestor - chimps oftenclaim to have stayed late at the office, while gibbons developed their enormously long arms just to tell fishing stories.
The programme took a mostly sensible approach to lying, with different angles from psychologists, priests, philosophers and fibbers. But even here, there was a touch of Kellner's PMT, with Sissela Bok, a moral philosopher, suggesting that we've always lied, but that in the last 20 years it's got far worse. Did she really think we'd fall for that one?