Believe the prime minister and it is morality, rather than economics, which requires him to cut taxes. In an important article in the Times last week that was factually incorrect, philosophically incoherent and economically bonkers, David Cameron set out the Tory credo. He was wrong on all counts. Trying to argue why every reader should vote Conservative, he instead revealed the darkness of the blind alley into which modern Conservatism has stumbled.

All Britain’s ills – a “ bloated, high-taxing, welfare heavy nation” – were rooted in a state that had grown too large because of an indiscriminate willingness to spend money that was not its own. This undermined incentives and, worse, it undermined morality. Only one sentence genuflected towards the moral good of the rich and able paying a “fair” share towards our “public services and safety nets”: the real enemy of morality was the principle of taxation itself.

“Every single pound of public money started as private earning,” he intoned. Building on what seems an uncontestable and homespun truth, he made the moral claim that because “every single pound of public money is private earning… what is morally wrong is [a] government spending money like it grows on trees”. Conservatives, we should understand, believed that every individual’s earnings should be treated as his or her own to which no government had a right. Labour, by contrast, were the immoral high spenders of other people’s money. It was a fundamental divide.

Thus the government, even while it had found “£100bn of savings in this parliament”, had cut income tax by £10.5bn. So rooted was the Tory belief in the immorality of taxation that in the next parliament he would find a further £25bn of saving – reassuringly little because most of the public deficit-cutting job was done – and a juicy £7.2bn of tax cuts. Tories were both moral – even in the middle of an austerity drive they cut taxes – and economically competent.

Except that the last claim survived just a few hours before being dismissed by the Institute for Fiscal Studies. There is “no sense”, declared its directors, in the claim that most of the deficit-cutting – some 80% – had been done. The prime minister, aping Tesco, had booked savings that were earmarked for the first year of the next parliament in the current parliament and then ignored savings that were planned for 2018/19 to double up on the appearance that most of the deficit-cutting pain was over. The IFS was too polite to call this what it was: a lie. For all his fiscal dissimulation, Gordon Brown never had the brass neck to go this far.

David Cameron, the self-appointed guardian of morality, would doubtless argue that it was a small lie to serve the greater good of a Conservative government and its commitment to the moral system of low taxation, small state and the individual virtue that goes with it. Thus will Britain flourish. But it won’t, because the core assumptions don’t stand.

Even in Tory land no man or woman is an island. Human beings associate in societies because of a primeval need and fundamental instincts. As evolving primates, we first learned to speak because it was more effective to hunt in groups that could communicate.

In 2014, we are similarly social, acting together to get the best results. The physical expression of this social necessity is our public institutions and the resources they deploy are properly created by a fee everyone pays: taxes. Those who earn more contribute more because proportionality of contribution represents another fundamental human appetite: fairness.

The economy needs public agency. The long commutes that Mr Cameron so celebrated in his article are done in publicly provided railways with fat public grants for the private companies that operate them. The innovations that make offices and factory floors competitive come from publicly funded science and public grants that allow companies and entrepreneurs to lay off some of the enormous risk of being technological pioneers. No significant innovation or invention has ever happened anywhere without public initiative at some stage in the process.

Economies and societies grow out of an interdependence between public and private: they need each other and taxation is the financial connecting rod. To echo the IFS, there is no sense in which “every pound of public money is private earning”: private earning becomes as high as it is only because of public investment. Taxes are the means by which we furnish public agencies the wherewithal to provide us with the universities, research, roads, railways, networks and all the rest that allow private companies to flourish. It is why the IMF, considering the best way to get public finances back on track after a credit crunch, recommends that governments try to preserve as much of that enterprise-enhancing public spending as possible, increasing rather than lowering taxes as part of the programme. Mr Cameron’s boast is economically illiterate.

Taxes are socially indispensable as well. “Public services and safety nets” are not inconvenient social burdens that require immoral taxes. They are created as a collectively owned means of guarding against the hazards and risks that every human might confront – of a crippling illness or disability – and problems associated with ageing.

We do not deserve what will or could happen to us, but we pay our taxes to fund systems that protect not just ourselves but each other. Taxation, in this sense, is the most complete expression of our morality. Of course the Treasury should husband our resources, not because taxation is immoral but because it has a duty to make sure this social money does as much work as possible, giving us the biggest return for our moral taxes.

In any case, it is a fiction that Britain does not flourish because of high taxation and a bloated welfare state; neither is high or generous by international comparison. We do not flourish because too many of our elite, faithful to Cameron’s false morality, do not want to acknowledge the crucial interdependencies on which economic and social success is founded, and thus their own obligations to pay tax.

We are invited to deepen an already failed experiment in libertarian individualism in which we each become selfish atoms in a social nothingness. Society should roar back its refusal to connive in its self-immolation. These Tories are just plain wrong.