More e-petitions will get written responses form the government, the Commons leader Andrew Lansley has announced. Any petition signed by more than 10,000 people, he says, will have a government response published alongside it. Well fine, for all the difference that is going to make.

There are three dozen petitions around that would qualify for such an official response, ranging from the culling of birds of prey to granting a pardon for Enigma codebreaker Alan Turing. But there are also a few joke ones, or perhaps barbed ones, like the petition calling for Mrs Thatcher's state funeral (when it happens) to be privatized. Very droll. But is it the sort of thing that parliamentarians should be racking its brains to respond to?

Petitions, like referendums, are a tricky constitutional issue. Yes, we want the public to be expressing their views strongly, and as Daniel Hannan and Douglas Carswell say in their excellent book The Plan [3] and other articles on opening up our system of government, it is right that Parliament should debate things that the public feel are important, rather than just things that the party leaderships think important. It makes our MPs recognise, once again, who they work for – not who doles them out ministerial jobs. So yes, peitions getting lots of signatures deserve some response and those with overwhelming support should be debated.

But we should not conclude from this that we should be governed by petitions. Nor even referendums.

Our representative system is a system of balances, albeit a rather creaky one. That is why we have two chambers of Parliament – so no dominant majority in the House of Commons can get its way. Not all the time, at least. As James Buchanan and Gordon Tullock showed in The Calculus of Consent, to impose your will on the public, all you need to do is to win 51% of the votes in 51% of the constituencies. So that's about a quarter of the population. Actually it is less, because only about half the population will probably vote anyway. So if there is just one chamber of Parliament, it is possible for quite small majorities to dominate the agenda. That is why we have such absurdly high tax on businesses and on people who earn a lot by creating jobs and prosperity. There are simply fewer of them than the majority, who enjoy the benefits of the taxation. Splitting the power with a second chamber, and indeed the Supreme Court, reduces that risk of the minority being exploited by the majority. Well, it reduces it a bit.

As Buchanan and Tullock suggested, and as I recounted in my recent book Public Choice – A Primer [4], we need strong constitutional arrangements to prevent this kind of exploitation. The US constitution managed to contain it for quite a time, but now it is hardly up to the job. As government has grown, the benefits of controlling the government – the amount you can loot from exploiting the minority – has grown too. So controlling governments has become big business. Ask any lobbyist. We need, in fact, surprisingly strong constitutional arrangements if we are to prevent the tyranny of the majority.

Am I in favour of democracy? Of course I am, but like the market economy, democracy only works if it is constrained by a set of rules. You need a fire basket to contain the fire. Without the rules of honesty, contract and private property, the market will soon descent into crony capitalism, with governments dishing out favours to their friends. Without constitutional rules to prevent minorities being exploited by majorities, democracy will turn into mere majoritarian populism, or into rotating elected dictatorships. Some people say this has already happened.