Japan's allergy to the nuclear option
Take a deep breath. Repeat after me: 'Japan is not going to develop nuclear weapons.' Repeat. Feel better? Yes, North Korea's nuclear test is a blow to the regional security order. It is a bitter defeat for diplomacy. And yes, Japanese - and mainland Chinese, Americans, South Koreans and others - are concerned about its implications.
But the fear that Japan will develop its own nuclear weapons, as a consequence, is pure fantasy. Japanese understand that the nuclear option is a last-gasp, desperate move that would create more instability and insecurity than it would eliminate.
To be sure, North Korea's test complicates Japan's national security planning and compounds popular insecurities. It also provides fodder for conservatives and nationalists who demand a more robust defence posture. It will be cited by Prime Minister Shinzo Abe and others as they campaign to revise Japan's constitution.
Over a decade ago, Tsutomu Hata, who was prime minister, acknowledged that 'Japan has the capability to possess nuclear weapons'. But capabilities alone do not determine a country's security policy; intentions are even more important.
Japan still lacks the will to develop nuclear weapons - and for very good reasons. Perhaps most powerful is the resilience of the nuclear taboo in Japan. The experience of the second world war is still strong in the popular consciousness, and the Japanese public remains highly allergic to the thought of developing its own nuclear weapons capability.
Japanese security planners recognise that a national nuclear arsenal would be destabilising, and would actually diminish Japan's security. Building a Japanese bomb would further erode the global non-proliferation order, generate greater mistrust among neighbours and prompt allies to question its strategic intentions.
This is the logic that animated former prime minister Yasuhiro Nakasone's recent call for a national study of the nuclear option. He is not endorsing that course: as he explained, 'the first priority is to continue being a nuclear-free state, and the second is to reinforce the system under the nuclear Non-Proliferation Treaty [NPT]'.
But he understands that a national debate on the subject would be good for Japan. Japanese must ask how a North Korean nuclear device changes the security landscape. It adds a new wrinkle, but it's hard to see it as a fundamental transformation.
The US nuclear umbrella is still in place, and it's unclear why deterrence wouldn't work against a North Korea with a tiny arsenal. After all, it worked well against the Soviet Union, which had weaponry capable of destroying the world several times over.
In fact, Japan has already studied the nuclear option. In the 1960s, a Cabinet-level group examined the possibility. Some three decades later, a study conducted at the behest of the Japan Defence Agency concluded that a nuclear arsenal made little strategic sense.
It would damage the country's image, undermine the NPT and prompt counter -measures by other countries in the region - including the development of their own nuclear arsenals.
Further, it could potentially threaten the alliance with the United States, while providing very little security for Japan, in return.
The country is so small, and the population so concentrated, that it would remain vulnerable to a nuclear attack even if there was a Japanese finger on a Japanese nuclear trigger.
That logic hasn't changed. A nuclear weapon wouldn't add to Japan's defence capability - but would do real damage to its core security interests. To their credit, the Japanese recognise that.
As Mr Abe explained to a Diet committee this week: 'We have no intention of changing our policy that possessing nuclear weapons is not our option. There will be no change in our non-nuclear-arms principles. We want to seek a solution through peaceful and diplomatic means.'
The only wild card is the US commitment to Japan's security. If Tokyo felt that Washington was wavering, then a homegrown bomb might make some sense. The answer, then, to growing unease after North Korea's test is continuing efforts to strengthen the Japan-US alliance - by both governments. To their credit, they are doing that, too.
Brad Glosserman is executive director at the Pacific Forum CSIS