This is just a short gripe about some of the commentary around the Labour leadership contest. So many who write about this express their puzzlement about how someone from the left of the party can suddenly appear to be so popular. This can only mean, they suggest, that the Labour party membership must have moved to the left. (For example this, from the FTs Jim Pickard.)
This mistake reflects something that Paul Krugman has remarked upon in the US: the tendency of commentators to define the centre as simply today’s mid-point between the two main parties. So as Labour moves towards the Conservatives, according to this way of looking at it the centre also moves to the right.
Now if that is how you want to define the centre, so be it. Such is relativistic view is very post-modern, I guess. But when that idea is then used to say that Labour party members must have moved to the left, its limitations become self-evident. In reality all that might be going on is that the views of Labour party members have not moved at all, but they have become left behind as Labour MPs and other prospective leaders have moved to the right. I think we have clear evidence that this is more likely to be what is happening. 
The most obvious example is the welfare bill, and Labour’s shameful decision to abstain on this. But another that is close to my heart is austerity. Talk to some, and being anti-austerity has become synonymous with being well to the left. Of course in reality it is just textbook macroeconomics, but if we stick to measuring everything on a left right axis, then remember that it was only as far back as 2009 that the need for fiscal stimulus rather than deficit reduction was the position advocated by a centre/left Labour party in the UK, and the Democrats in the US. It cannot be surprising, therefore, that among a relatively well informed electorate that is the Labour party membership an anti-austerity position is still seen as a sensible policy. With an extreme relativistic view you could say that by sticking to this position these people have moved to the left, but please don’t appear surprised that this has happened.
 It is equally fallacious to think that those who vote for Corbyn agree with every one of his policies. Some of his popularity may be a form of protest not just at the policies of his competitors, but also their style: see the clip in the middle of this typically amusing article by Mark Steel.