Many years ago, a Foreign Office grandee of an older generation, Sir Julian Bullard, used to tell aspiring new diplomats that the best reason for learning German was to read Nietzsche’s epigrams. I’m not sure many of them took his advice to heart, but I did at least read the one that says Wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein, which translates as: if you look long into an abyss, the abyss also looks into you. Another word for abyss is, of course, Gulf.

Things are changing in the Persian Gulf region. An elderly, ailing Saudi king dies and is replaced by his elderly, ailing half-brother – just as Houthi rebels appear to achieve a major success in Yemen. Meanwhile, representatives of more than 20 countries – including Britain, the US and Iraq – agonise over how to tackle Islamic State (Isis), with Baghdad seeking more support from its western allies for the fight.

Faced with so much change in the Middle East, western governments seem to be at a crossroads. Not so long ago, we were intent upon a bombing campaign to remove the Assad regime in Syria. Now, only 18 months or so later, the continuation of that regime appears to be a necessity – if a rather distasteful one – for western policy in the region, if the much more dangerous threat from Isis is to be contained or removed.

At the same time our attitudes to Iran have also shifted, as the process of negotiation over the Iranian nuclear question has ground slowly forward. I was surprised last week to hear a colleague suggest that the idea that Iran was a force for stability in the Persian Gulf region was now conventional wisdom. But our attitudes have not shifted enough for us fully to embrace the Iranians as allies in Iraq and Syria. That’s a perverse situation. And there are still influential voices in the US and elsewhere who, like the Saudis, warn of Iranian expansionism.

Those same voices have tended to laud the alleged reforming zeal of King Abdullah (nothing I have heard leads me to think his successor will be any more zealous), ignoring the uncomfortable fact that most of the worst Islamic extremism and terrorism of the past two decades has tracked back, through funding and religious influence, ultimately, to Saudi Arabia. In this situation, the state we have been accustomed to seeing as our enemy (Iran) is starting to look more like a potential friend, and the state we treat as an ally looks more and more, if not like an enemy, like the sort of friend that renders it unnecessary to have enemies.

It would almost certainly be unwise to expect too much of a possible alliance with the Iranians in fighting Isis. We should be fully alive to the range of opportunities opened up by the developing rapprochement with Iran; it is one of the few bright spots in an otherwise dark picture. But the Iranian armed forces are not powerful as others in the region in terms of big battalions; their Revolutionary Guard Corps is experienced and highly competent, but they could probably not do much more than they are doing already in Iraq and Syria.

Even if they could help, it would probably not be in the interests of long-term stability, because heavy intervention by Shia Iran in Iraq and Syria would probably only incite further resistance from Sunni Arab groups. The key to success against Isis has to involve encouraging Sunni Arabs themselves to reject Isis, as they rejected and fought al-Qaida in Iraq in coordination with the so-called US surge from 2007 onwards. Unfortunately, western support for, and relationships with, those Sunni Arab elements dwindled after the success of that policy, and that is partly why we have Isis. Rebuilding those relationships now is going to be difficult because the Sunnis feel the west betrayed them.

In articulating our policy in the region, in circumstances of sharpening sectarian divisions, it is all the more important that our commitment to stability is clear and unequivocal – particularly our commitment to the extirpation not just of Isis and al-Qaida but also, as far as possible, of the causes that brought them about. This is where I come back to Bullard, and to Nietzsche: the Persian Gulf looks also into you – in other words, the tensions of the region require us to re-examine our own policies.

Stability in the Persian Gulf region is what we say we want, and much analysis and commentary takes that as a given. But do we really? How much do we want it? Do we want it enough, for example, to risk alienating our ostensible allies along the Gulf’s southern shore, and changing their disposition toward lucrative weapons purchases? Because that is what would happen if we were to tackle head on the role some of the countries play in funding the most radically destabilising Sunni extremist groups, such as Isis and al-Qaida.

Many would agree that the extremist Sunni ideology of Isis is merely a step on from, or the application of, the Wahhabi Islam that is the basis of Saudi Arabia. It is this extremism that is driving the burgeoning sectarian conflict between Sunni and Shia, potentially disastrous on a hitherto undreamed-of scale.

Or do we instead, whatever the window dressing, calculate that our national interests, in the narrowest sense, are entirely about arms sales to Saudi Arabia and other Gulf states? Do we turn a blind eye to the extremist sympathies and funding that flows from them, and in effect allow these states to buy our foreign policy along with our weapons? Buy one, get one free.

Julian Bullard would not, I think, have recommended the latter course. It should be plain enough that to throw in our lot on one side of a sectarian conflict in the Middle East could have catastrophic consequences both for regional stability and for our own interests. But it seems as though that is the drift of the policy thinking of at least some elements of the present government. If the UK, in particular, is to have any credibility in the future in this region, they must be restrained.