By Gideon Rachman, Financial Times

Sitting in the front room of his suburban house in Delhi, K. Subrahmanyam, the doyen of Indian strategic thinkers, sips some tea, coughs a little - and remembers the moment he decided that India must develop nuclear weapons.
"It was on a visit to America in 1968," he recalls. "I saw all the top strategic thinkers. Kissinger, who was still at Harvard at the time, Schelling; it was after that, that I decided we must have the bomb. As a matter of national survival."
Some 40 years later, India is on the brink of becoming an accepted member of the nuclear-weapons club. Manmohan Singh, India's courtly and academic prime minister, met President George W. Bush at the White House.
This unlikely couple shook hands and congratulated each other that the US-India nuclear deal has passed the Indian parliament and been accepted by the international Nuclear Suppliers Group. Eventual approval by the US Congress seems all but inevitable.
Under the deal, the US will drop its efforts to punish India for developing nuclear weapons - which were introduced after the country staged a nuclear test in 1974.
India will now be able to buy nuclear material for civil use and - its critics fear - for the manufacture of more nuclear bombs.
This development has been greeted with horror by many experts on nuclear non-proliferation. Respectable opinion in the form of The New York Times, the Financial Times and The Economist has condemned the deal. Jimmy Carter, the former US president, has said that it "puts the world at risk".
But, in fact, it is the right decision. The US-India nuclear deal is simply a recognition of reality. First, that India has nuclear weapons and is not going to give them up.
Second, that India is going to be one of the great powers of the 21st century - and that it makes sense for the US and the West as a whole to move beyond a futile effort to sanction the country into renouncing the bomb.
It is, of course, unfortunate that nuclear weapons and great-power status should be so closely associated - but there is undoubtedly a link.
The five countries that are allowed to possess nuclear weapons under the Nuclear Non-Proliferation Treaty also happen to be the five permanent veto-wielding members of the UN Security Council - the US, Britain, China, France and Russia.
All other signatories to the NPT are allowed only civil nuclear power. India has long refused to sign the treaty, in protest at this "nuclear apartheid". Like Pakistan and Israel, it chose to develop nuclear weapons outside the framework of the NPT.
It would certainly have been preferable if India's status as one of the world's great powers had been recognised with permanent membership of the security council.
Jaswant Singh, India's foreign minister at the time of India's 1998 nuclear tests, recalls with a laugh that Madeleine Albright, then the US secretary of state, asked him if India was "trying to blast its way into the P5? I said, 'No, but we have surely woken you up'."
Indeed, one of the baffling and slightly alarming aspects of India's development of nuclear weapons, is that its motives are not entirely clear. Is the main country to be deterred, Pakistan or China? Are India's goals strategic or symbolic? Does India want the controls on nuclear trade lifted for commercial or military reasons?
America's goals are similarly unclear. Was Bush mainly motivated by a desire to build a strategic relationship with another of the world's great democratic nations? Is this part of a US strategy to counter-balance the rise of China? What part has industrial lobbying played in the decision?
Even if you ascribe the most benign combination of motives to both parties, there are still plenty of critics who will argue that the deal is dangerous and hypocritical.
It is dangerous because it blows a hole in the nuclear non-proliferation regime, just as the world is struggling to prevent Iran from developing nuclear weapons.
And it is hypocritical for the US to insist on the strictest enforcement of the NPT when it comes to Iran, but to cut India a sweetheart deal.
The problem with the danger argument is that the NPT has hardly been an infallible barrier to nuclear proliferation. China, which has signed the treaty, has spread the technology to Pakistan. India, which has not signed the NPT, has not proliferated - and nor has Israel, another non-signatory.
Meanwhile, loopholes in the treaty allow countries such as Iran and North Korea to get right up to the edge of nuclear weapons - and then to withdraw from the treaty, if they so choose, and develop weapons legally.
As for hypocrisy - well, there is a lot of it about. But, in fact, the Indian and Iranian cases are legally different. India never signed the NPT. Iran did - and so it is obliged not to have a nuclear-weapons programme.
In any case, this is a question of political reality - as well as of law. India already has nuclear weapons and nothing short of a global disarmament treaty is likely to change that fact. Iran does not yet have the bomb, and it is important to try to prevent it from reaching that point.
All the more so, since the nature of the Iranian and Indian governments is clearly very different. India is a status quo power and a settled and secular democracy; Iran is none of the above.
Bush may be disappointed if he thinks that, after his nuclear favour to Singh, India will be reliably pro-American from now onwards. But the US president is still doing the right thing.