Our political system is dysfunctional. It selects for the incompetent, the dishonest and the downright deluded.

So much is obvious to those who care to think about it. What's not so obvious is that there is a more subtle bias in politics which distorts and diminishes political debate.

Recall that all institutions are selection devices: they select for some people and ideas and against others by filtering out some types and by disproportionately attracting others. Even if we had a well-functioning system which selected against crooks, fools, narcissists, egomaniacs and sociopaths our politicians would still be unrepresentative of the people, even of educated and informed people.

To see this just ask: what sort of people are attracted to political careers?

In a well-functioning polity, the answer would be (and in fact is for many MPs now): those who think politics matters, that it can make a difference. If you think it can't - either because a £2.5 trillion economy is hard to change, or because the power of capital constrains reform, or whatever - you'll choose a different career.

And what sort of folk think that politics can make a difference?

Those who are overconfident - if not about their personal abilities then about the potential for small policies to have large effects; or about the ability of policy-makers to escape the constraints imposed by capital; or about their ability to overcome bounded rationality and knowledge; or about the potential for "good chaps" to stay in charge of government.

Such overconfidence will have systematic effects. It will lead to a neglect of the need for policies and institutions which are resilient to error so it will (for example) underweight the need for automatic stablizers in the belief that policy-makers are smart enough to use discretionary policy to prevent recession. It will cause them to favour tricksy policies such as tax credits or corporation tax over simple ones such as a basic income or land value tax because they over-rate their ability to design and implement complicated policies. It will cause a bias towards belligerent foreign policy by underweighting the risks of intelligence or military failures. And there'll be a bias against freedom because, as Hayek said, "we will rarely know what we lose through a particular restriction of freedom" - and overconfident policy-makers will not be awake to the limits of their knowledge.

Closely related to the faith in policy is a belief that the economy and society can be managed from the top down whilst under-appreciating the importance of complexity and emergence. Marx thought that "the emancipation of the working classes must be conquered by the working classes themselves" - that socialism would be an emergent process. Parliamentarians, by contrast, have been squeamish about such agency. As Ralph Miliband put it, they have "treated the voters not as potential comrades but as possible clients." Labourism, says Phil Burton-Cartledge "was born for the compromises, Byzantine procedures, and plodding constitutionalism of the House of Commons."

In the party, this has for years meant a hostility to "extraparliamentary" action. As Miliband put it in Parliamentary Socialism:

The leaders of the Labour Party have always rejected any kind of political action (such as industrial action for political purposes) which fell, or which appeared to them to fall, outside the framework and conventions of the parliamentary system. The Labour Party has not only been a parliamentary party; it has been a party deeply imbued by parliamentarism.

This is echoed today in Starmer's ambivalence towards railworkers' strikes.

It also means the party has accepted managers' right to manage. We saw this particularly in Gordon Brown's acquiescence to bosses in the belief - refuted by the financial crisis - that they had especial skills of foresight and control. And as Phil says, for Labour economic issues have traditionally been "about 'fairness', not contesting the employer's right to run matters as they see fit." The party has long been wary of economic democracy for this reason.

For the same reason politicians also have a bias against free markets because these too are emergent processes; the creation of private sector monopolies is not, remember, the same as the creation of a market.

Not that this under-weighting of emergence is confined to Labour. Far from it. It is one of the more egregious examples of BBC bias. The BBC has long neglected slow-moving emergent processes such as the productivity stagnation and has failed to see that government borrowing is the counterpart of private sector decisions to save or (not) invest: it is emergent.

This overconfidence in top-down control can have fatal effects. The Chilcott report found that one reason for the failure of the Iraq invasion was that over-optimism "can prevent ground truth from reaching senior ears."

Sometimes, however, it is through small windows that we see a big picture. So it is here. Politicians and political journalists are avid consumers of political biography and have less interest in the social sciences. That fits with overweighting the potential for "great men" to change events whilst underweighting socio-economic forces.

There's something else. The problem with politics is that, to paraphrase Michael Walzer, it takes too many evenings. Professional politicians must attend to their constituents and various hobbyists with bees in their bonnets. They are therefore selected to be busy cunts, to borrow Jaap Stam's famous description of the Neville brothers. It's no surprise, therefore, that all politicians value "hard working families" and neglect Bertrand Russell's essay in praise of idleness. Nor is it surprising that they regard increasing numbers of over-50s leaving work as a problem rather than as something to be celebrated - people being liberated from drudgery and hierarchy.

If your evenings are consumed by political meetings, you can't go to concerts,watch TV or read. Politics will therefore select for philistines. Hence the cuts to arts funding; squeezing of music and arts out of schools; and destruction of adult education.

My point here echoes Peter Allen's The Political Class. Politicians are unrepresentative not just because they are disproportionately male, stale and pale but simply because they are politicians. All professions tend to have a partial and distorted view of the world merely by virtue of attracting particular types and developing particular ideas and dispositions. Politicians are no different.

Except, I suspect, that it is harder for them to see it. The tendencies I've described aren't confined only to MPs, but also to many political journalists and the talking heads who appear on those speak your branes shows. They are therefore reinforced by echo chambers and groupthink. Fish don't know they are wet.

This is not to say this view of the world is wholly wrong. It's not: sometimes moderate top-down reforms do work. Nor is it to say that all MPs and political journalists share all of these dispositions. They don't; it's just that they are more prevalent among the political class than the general educated public.

And - what is important - this would be the case even if there were no nepotism in journalism or rigging of the choosing of parliamentary candidates, and even if politicians were intelligent, rational and well-intentioned. It's simply the result of selection effects - effects which are inherent in even the best-functioning representative democracy. Which is why there's a case for considering alternatives such as sortition and deliberative democracy.