Members of Parliament can face no bigger decision than the decision on whether or not UK forces should take military action.
Our Parliament must ensure it takes decisions in the interests of the security and wellbeing of our citizens and must consider the impact of our decisions on the wider world.
In the aftermath of unforgivable atrocities in Paris and around the world, the Prime Minister is recommending that the UK bombs Syria.
We must accept that decent, principled MPs can get it gravely wrong on international issues and military issues - especially in the aftermath of terrorist attacks and especially when confronted with a humanitarian crisis. Few now dispute that our Parliament got it gravely wrong when deciding to invade Iraq. And I believe that, more recently, our Parliament got it gravely wrong when deciding - with only 13 MPs voting against - to take military action in Libya.
I am not a pacifist but I believe that if our Parliament decides UK forces should bomb Syria, then our Parliament will be making another grave error. There are, as President Obama has said, 'unintended consequences' to taking military action.
I do not believe that dropping bombs into the multi-sided civil war in Syria will make British citizens safer from terrorist attacks. I do not believe that UK bombing a second country stops murderous terrorists from walking into a shopping centre, a tourist resort or a concert hall in a third country - or in the UK itself - and carrying out unforgivable atrocities. For example, I do not believe that bombing Syria would have stopped the horrors in Paris or, earlier this year, in Tunisia.
We all wish to see an end to the war in Syria and end to terrorist attacks. We all want peace to be achieved in the Middle East and in the wider world.
The decision facing our Parliament is whether UK military action in Syria now can deliver that.
I believe that the Prime Minister has not demonstrated that sufficient lessons have been learned from UK military action in Afghanistan, Iraq and Libya. And I am not persuaded that the UK bombing Syria will deliver increased security for the UK and our citizens.
There has been war in Syria for four years already. The Prime Minister is asking MPs to agree to joining that war with the commitment that British forces would 'sustain our role in the campaign for as long as required to get the job done'. This is a recipe for a long-term commitment to military action.
The Prime Minister is also asking MPs to support action against ISIS but with a clear view to 'regime change' for the country as a whole, by operating on the same side as his claimed 70,000 'moderate' anti-government fighters. Who these fighters are and how 'moderate' they are remains unclear. And it should not be forgotten that it is not too long since the same Prime Minister who is now asking Parliament to decide to bomb ISIS was asking Parliament to bomb Assad, which would have assisted ISIS.
It is inevitable that civilians in Syria will be killed by the bombing that the Prime Minister proposes. There is also a very real risk of British forces operating in a conflict zone where they could end up clashing with Russian forces. All of this will not make British citizens safer, but will instead risking spurring on the increase of terrorism and the threat of a widened conflict.
To bring an end to this growth of terrorism which is a threat to our national security, the Middle East and the wider world, we need to ensure Turkey and Saudi Arabia do not assist or enable terrorism. The Prime Minister states that his priority is to defeat ISIS but the Government seems to be turning a blind eye to the sources of ISIS weapons and finances.
Instead of joining in this multi-sided civil war, as the Prime Minister proposes, Britain should support the international efforts to end the civil war in Syria. ISIS must be militarily defeated but are British planes the best way to do that? I fear that - given the UK's terrible record in the region - British air strikes will feed the ISIS narrative that the West are 'crusaders' against the Muslim world. ISIS's military defeat has to be delivered by the part of the world in which they operate. We cannot allow a band of murderous terrorists who committed unforgivable atrocities in Paris to force the hand of the British state. Their terrorism should not dictate our foreign policy. It is my belief that the ISIS would be delighted to lure Britain in to the multi-sided civil war in Syria.
I am not persuaded that the UK bombing Syria is the right thing to for Syria, the wider region or for Britain. I hope that our Parliament doesn't again make a decision that it - and the wider world - subsequently regrets.