To bomb or not to bomb? The controversy rolls on.
But increasingly David Cameron believes that he can get a majority in the House of Commons to extend Royal Air Force operations from Iraq to Syria.
At present RAF planes are bombing selected targets in Isis territory in Iraq. But they are also operating over Syria.
They are conducting reconnaissance and intelligence operations.
They are assisting the coalition of Arab states, the USA, the French and others.
The one thing they are not doing is taking part in military operations to destroy Isis and its capabilities in Syria.
The border between Iraq and Syria is simply a line drawn on a map. It is impossible to define except perhaps by the use of GPS.
When the House of Commons gave David Cameron support for the RAF’s present activities 14 months ago there were some, including myself, who pointed out the illogicality of treating Iraq and Syria as if they were visibly and geographically separated.
The question which must now be answered is whether there is justification to change policy and to expand the role of the RAF in Syria.
Some say we should not under any circumstances do so.
Others say military action would only be justified if it had express UN authorisation in a new resolution.
When asked what we should do both camps say we should continue to try to achieve a diplomatic settlement in Syria which results in a change of government and ultimately the departure of Assad.
I am all for diplomatic initiatives to replace Assad.
In recent conversations between Russia, the United States, France and ourselves, there has seemed to be a glimmer of a chance of an agreement.
The terrible events in Paris have concentrated minds as has the destruction of the Russian airliner from a bomb probably placed in its luggage compartment.
A diplomatic settlement will not be easy but without it there will be no long-term stability. It must be a settlement in which Iraq and Syria and their neighbours have confidence.
But a diplomatic solution, however desirable, will not be enough.
Who believes those who control Isis, whose policies include beheadings, ethnic and religious cleansing, slavery and the systematic degrading of women, could be persuaded to join in any political settlement?
What could the allies in all conscience offer Isis?
A settlement may be achieved if Isis is so reduced in effectiveness that they can be marginalised.
How is that to be done?
I’m afraid only by military means.
By destroying their military capability and wresting away their hold of territory. By undermining their apparent invincibility.
It can’t be done from the air alone but combined operations can create conditions in which it may be possible.
Better equipment and training for the Iraqi army. Better cooperation with the Russians. Support for the Kurds who have proved the best ground forces against Isis.
Can we justify it legally?
In my view, yes.
The Security Council has already passed a resolution urging the use of “all necessary means” (the language used in UN resolutions when authorising the use of force).
Neither Russia nor China vetoed that resolution.
Here at home the threat level is set at “severe”, the second highest level, which acknowledges a terrorist attack is likely.
The security services have foiled seven terrorist plots. Our close neighbour and ally France has been brutally attacked.
And Isis continues to make threats against the United Kingdom and its citizens.
There are sufficient legal grounds to justify the United Kingdom acting in self-defence and attacking Isis both in Iraq and Syria.
The existing UN resolution and the threats to the United Kingdom are a sufficient justification.