Ten years ago, I watched in dismay as MPs voted for the Iraq war. Last week I watched in dismay as they voted against possible military intervention in Syria.
On each occasion, the question uppermost in my mind was about this country's values.
We believe in universal human rights; our laws, treaties and political leaders say so.
In the recent past we have intervened to stop atrocities in Sierra Leone, Kosovo and Libya.
Iraq is a different story, but no-one seriously doubts that horrors are being perpetrated in Syria: as MPs voted, footage was emerging of another dreadful attack by Bashar al-Assad's forces, a fighter jet dropping an incendiary bomb on a school in Aleppo.
Opponents of intervention ask why Assad would sanction the use of such terrible weapons when UN inspectors were in the country. This is to misunderstand the nature of the regime, which has repeatedly displayed its sense of immunity.
Assad knows Russia and China will veto critical resolutions at the UN Security Council.
He lived in the UK until 2000, his wife's family have lived in London for years, and he understands the toxic legacy of the Iraq war on public attitudes.
Toxic and paralysing, to judge by last week's votes, when some MPs seem to have been influenced more by the events of 2003 than 2013.
Syria is not Iraq.
The Iraq war was based on a disastrous fiction – the claim that Saddam Hussein posed an imminent threat to the world, whereas his regime was actually weaker than it had been for years.
The human rights case for regime change was compelling, especially after Saddam used chemical weapons at Halabja, but it barely figured in 2003.
There's a massive irony here: we went to war against a tyrant who turned out no longer to have weapons of mass destruction but won't consider limited air strikes against one who has used them in recent days.
President Obama's Secretary of State, John Kerry, is sure that Assad's forces launched the chemical attacks on Damascus 11 days ago. For all its flaws, the Obama administration is not the same as the Bush White House.
A gap has opened up between this country's rhetoric and the way MPs voted in the Syria debate.
I don't deny that such ventures are risky, but the consequences of refusing even to consider an intervention are worse: the coalition against Assad is fractured, Obama's position has been made more difficult and we have signalled our impotence in the face of the use of banned weapons.
Military intervention on humanitarian grounds was championed by Robin Cook before ghastly Blair took it up.
It is an imperfect response to the mass slaughter of civilians, but consistent with our stated aim of upholding universal values.
What happened in parliament last week is a mess.
It's often said that those who fail to learn from history are doomed to repeat it. Learning the wrong lesson is even worse.