I remember that Howard Dean, briefly a contender for the Democrat presidential nomination, once said - or was it his adviser, I forget - that politicians need to go off message if they are going to come across as authentic.
This seems to me to be overwhelmingly true. The politicians we trust are relatively uncontrollable. But there is more to authenticity in politics, and part of it is the paradox of compromise.
Politics is all about compromise. But it isn't just about compromise. And therein lies the dilemma for the Lib Dems, and anyone else who really believes in diversity and the necessity of working with people you don't agree with.
Because politicians who just believe in compromise tend to come across as inauthentic, slippery and mildly devious. To make compromises possible, they have to be real - which means they have to be uncompromising and clear about they believe. They have to be clear about what they want.
This is all a way of congratulating the party for sticking to what they believe about runways in the south east, and about air travel generally.
Rather unexpectedly, Duncan Brack demolished the amendment designed to open the door to a runway at Gatwick - during the debate on the party's pre-manifesto in Glasgow - and did so overwhelmingly.
Party managers are worried, of course, that the vote will look like a betrayal if future coalition negotiations end up forcing some kind of agreement on the Gatwick runway. This is certainly true (though it suggests that maybe they would have been wiser not to have brought it up in the first place). But if the party pre-negotiates its position on everything beforehand, the even greater danger is that it will end up with a flabby set of compromises - with no authenticity.
I do find it bizarre that the political establishment has simply accepted the airport lobby case that they need new runways. There has been little or no resistance from an economic point of view - no examination of Heathrow's bloated operation, no genuine study of needs and wider costs.
So, yes, I'm proud of the Lib Dems for refusing the kowtow. There will be no end to airport expansion in the south east - a kind of driver for economic centralisation - unless we take the political decision to stop. Otherwise every extra terminal needs another one, every extra runways means pressure for one more.
Wander around the impoverished neighbourhoods of Southall, under the relentless Heathrow flight path, and you will be able to see the sacrifices we force on the poor - now and, all the more, as the climate changes - just for more intensive reliance on air travel..
Which brings me to the climate change debate. Nothing is so depressing than the failure of humanity to rise to the challenge of tackling a changing climate.
In fact, it is so depressing that I'm beginning to wonder if the political language has to change too. I detect a reluctance to use the term, to join in the debate at all, for fear of revealing ourselves as angry pessimists - authentic, perhaps, but in the wrong way.
But if we need to change the dialogue on climate change - to shift to reducing our wasteful energy, to providing prosperity more widely - we shouldn't assume that somehow we forget about the original objectives. However you describe it, extra runways - yet more take-offs and landings to feed the huge shopping centres of Heathrow and Gatwick - is a staggering waste of resources.
Lib Dems may not get the seats they need to resist successfully, but it is at least authentic to set out what you believe. And they have.