I've long said that support for capitalism and tolerance of inequality is founded in part upon cognitive biases. But I wonder: could it be that support for Corbyn is also based in part upon such biases?

I'm thinking of at least four different ones.

One is wishful thinking. Paul Mason says these are "days of hope" for the left because "neoliberal capitalism is busted, discredited and on life support." I agree that neoliberalism is discredited. But so what? Politics is about power not intellectual validity, and bad ideas can remain dominant for a long time. What's more, the backlash against neoliberalism seems to be taking the form not (just) of leftism but of the sort of reactionary anti-immigrant sentiments that gave us Brexit.

Granted, Paul is right to take heart from the fact that "people are flooding into a left-led Labour party". But how important this proves to be rests upon network effects which seem to me to be uncertain. If the new members help to persuade floating voters to support Labour - either through conventional leafleting and canvassing or simply though day-to-day conversations in pubs and workplaces - then there are grounds for hope. But if they are just a circle-jerk of clicktivists there aren't. Corbyn's awful poll ratings aren't yet sufficient to adjudicate this issue, because the process of day-to-day conversations will take a long time to work, if it does at all.

Secondly, there's a false consensus effect. It's easy to look around one's circle of like-minded friends, and at the hundreds of people at Corbyn's rallies, and infer that one is part of a mass movement. Of course, opinion polls controvert this belief, but as David Hume famously said the impressions formed by our own experience are more forceful and vivid that mere ideas and second-hand reports.

Thirdly, there's the confirmation bias, or a form of post-purchase rationalization. Having backed Corbyn, there's a tendency to interpret ambiguous evidence as supportive of one's decision. So, for example, his supporters put great weight upon his achievements - shifting the party leftwards and building a mass membership - and downgrade the many stories of his personal incompetence as leader.

Fourthly, there's the poisoning the well fallacy. Yes, many of Corbyn's enemies are careerists, Quislings and idea-free triangulators (it would be unfair to call them technocrats as they have no technique). But this does not mean that all their complaints about him are wrong. To discredit all these complaints because they come from "Blairites" or "red Tories" is to commit the fallacy of poisoning the well.

The combination of the confirmation bias and poisoning the well fallacy generate asymmetric Bayesianism - a tendency to overweight evidence for one's prior belief and downgrade contrary evidence.

Now, I'm aware that in saying all this I risk being accused of seeing cognitive biases everywhere. As the old jokes go, we're all guilty of the false consensus effect, and since I learned about the confirmation bias I've seen it all the time. Nevertheless, it would surely be a remarkable accident if errors of judgment were found only on the right. It seems to me that, in some cases, the passionate support which Corbyn attracts is disproportionate to the evidence of his merits - evidence which, I stress, isn't wholly absent.

There is, though, a problem here, of which rightists remind me every time I claim that capitalism is sustained by cognitive biases. It's that we can sometimes reach the right conclusion via flawed reasoning: just because you're irrational doesn't mean you're wrong. Is this the case with Corbyn? I confess to be being unsure.