Jess Phillips thinks she'd be a good PM. I tweeted this morning that this is more a sign of her overconfidence than it is of her ability. I did so for two reasons.

First overconfidence, whilst not universal (pdf), is widespread among those in prominent positions. Underconfident people don't apply for such jobs, unless pushed, and so are filtered out whilst there is no similar filter against the overconfident. Quite the opposite. Hirers tend to mistake overconfidence for actual ability and so hire the overconfident: one can easily imagine Ms Phillips fluent confidence making a good impression at her CLP.

My base rate probability, therefore, is that Ms Phillips is expressing an opinion typical of MPs - or at least those who court publicity - rather than giving us a diagnosis of her actual ability.

Overconfidence, though, can be hugely damaging. Daniel Kahneman has called it the most dangerous of all cognitive biases. The three worst decisions in the UK in the last 20 years - Blair's war in Iraq, RBS's takeover of ABM Amro and Cameron's calling a Brexit referendum having created the conditions in which he might lose one - were all motivated in large part by overconfidence.

A useful corrective here has been provided by Charlie Munger. It's important, he says, to know the edge of your competence - to know what you're good at and what you're not.

There's a second reason why I think she's being overconfident. It's that the honest and true answer to the question: "would you be a good PM?" is "I don't know."

Ole Gunnar Solskjaer shows us why. His CV as a manager is vastly inferior to Jose Mourinho's, comprising a mediocre spell at Cardiff and some success in a third-rate league. But he seems to have transformed Manyoo. This is because Mourinho was a terrible match for the Manyoo job: his brand of safety-first football was ill-suited to a squad of young attacking players and to a fanbase that expected expansive football. Solskjaer on the other hand is a much better match.

This applies to many top jobs in business and politics: what matters is not just somebody's strengths and weaknesses but rather the match between these and the job requirements. If a company's problem is poor cost management, for example, it needs a cost-cutter as CEO rather than a marketing man, and vice versa. As Boris Groysberg has shown (pdf), what matters for corporate performance isn't so much a bosses' CV as the match between his strengths and the company's needs.

Winston Churchill's life embodies this point. He was a terrible match for the job of First Lord of the Admiralty in 1915 and for the job of Chancellor (pdf) in 1925. But he was the right match for the position of PM in 1940.

Which is why we cannot say whether Ms Phillips would be a good PM or not, leaving aside her personal policy preferences. For any complex job we must ask what qualities it requires and what personal weaknesses can be forgiven or glossed over, and we must then ask who fits those strengths and weaknesses. Churchill was a great PM in 1940 because we needed his belligerence. Cameron was a disaster because his overconfidence was misplaced, and May is doing badly because her lack of interpersonal skills is a terrible weakness when we need a good negotiator.

But we don't know what exactly the job requirements of PM would be at the time when or if Ms Phillips becomes a plausible candidate for the job. She might make a good PM. Or she might not. It depends upon the circumstances.

Herein lies one of my (many) beefs with politics. Many people don't think this way. Instead, they have a cargo cult mentality. We saw this in the recent row about Churchill: too many wanted to see him as either hero or villain and not as what he was - sometimes the wrong man for a job, and sometimes the right. Too many people think a great leader will transform an organization without asking what the mechanism is or whether what makes a great leader is context-dependent. Churchill and Attlee were both great PMs, despite having utterly different characters: they were good matches for what was needed at the time. Many people rightly deplore the cult of Corbyn. But they themselves fall into a similar error. I've called Bonnie Tyler syndrome - holding out for a hero.

The truth is, though, that there are no heroes - or at least we cannot rely upon one turning up. All we can look for is to put round pegs in round holes. And this requires sober analysis, not wishful thinking.