Iraq's invasion and its aftermath illustrate Lord Salisbury's maxim about the 'optimist view of politics', which 'assumes that there must be some remedy for every political ill, and rather than not find it, it will make two hardships to cure one'. The Chilcot inquiry into the 2003 war in Iraq is a world away from the whitewash obligingly thrown over the venture by Lord Hutton's 2004 report, commissioned by Tony Blair while still in office. Sir John Chilcot's summary findings mount a cumulatively devastating critique of Blair's conduct before, during and after the war.

Chilcot finds that Blair overstated the case for war and in particular the imminence of any threat posed by Saddam Hussein. There was no urgent reason for invasion in March 2003; the containment policy, including the work of Hans Blix's UN weapons inspectorate, could and should have be allowed to continue. Cabinet was scanted; intelligence and legal advice distorted. Blair caved in too easily to US impatience to launch the war; plans for its aftermath were grossly inadequate, as were resources for British postwar occupation.

The optimist view is particularly dangerous when stiffened by moral purpose. Soon after the 9/11 attacks, Bush and Blair resolved to answer jihad with crusade. They chose to target a third party, with a fine disregard for the consequences: 'We don't do body counts,' the US general Tommy Franks said of the war in Afghanistan in 2002; you don't count the dead when God's on your side. Iraq Body Count estimates that there have been 251,000 violent deaths in Iraq since the 2003 invasion – a conservative figure beside other projections. An IBC graph shows the dramatic rise from the civilian death count in January and February 2003 – three and two respectively – to the unbroken run of hundreds, and often thousands of deaths per month since the invasion in March that year.

Chilcot does not say in terms that Blair lied about Iraq's possessing weapons of mass destruction. That charge is often made, but it's never seemed to fit Blair's highly moralised self-image. Blair's claims about Iraq's WMD up to March 2003 are closer to Harry Frankfurt's notion of bullshit, defined as assertion without regard to the truth of what's said. People bullshit for various reasons, but one is the moralistic urge to believe something regardless of whether it's true. As Frankfurt says, 'bullshit is a greater enemy of the truth than lies are.' Chilcot says that the Joint Intelligence Committee exaggerated the imminence of the threat, a point which formed the basis for Blair's buck-passing sorry-not-sorry apology last October.

A case against Blair (or George W. Bush) in the International Criminal Court is a non-starter, for reasons outlined by Geoffrey Robertson recently, since crimes of aggression were not defined by the ICC statute at the time of invasion and can't apply retroactively. Chilcot's remit excluded considering the war's legality. He did remark in his public presentation of the report that the invasion, though purportedly upholding the authority of the UN, in fact did the opposite. One possible legal avenue is a common law action for misconduct in public office, defined by the Crown Prosecution Service as an offence committed when 'a public officer acting as such wilfully neglects to perform his duty and/or wilfully misconducts himself to such a degree as to amount to an abuse of the public's trust in the office holder without reasonable excuse or justification'.

There is a case to answer. Since the war, Blair has stressed regime change as the rationale for aggression against Iraq, rather than the WMD which furnished the casus belli at the time. This is false. On 25 February 2003, Blair said in the Commons: 'I detest his regime but even now he can save it by complying with the UN's demand' (even though it was accepted by all but the coalition chiefs that UN Resolution 1441 wasn't sufficient for military action). Lord Goldsmith, then attorney general, originally advised that the war was illegal, then U-turned. Blair did not tell the Cabinet this. Goldsmith told Chilcot he didn't know why he had changed his mind.

Goldsmith, like a number of others, comes in for criticism, but Chilcot's finger of blame points squarely at Blair for the Iraq catastrophe. His response this afternoon to Chilcot accepted responsibility 'without exception', but also, bafflingly, without 'excuse' either, as in the old beaten football manager's line: 'I'm not making any excuses, because we were without five key players.' Blair had acted, in the all-absolving phrase, 'in good faith'. A catch in his voice, he sounded like a little boy who's had his catapult confiscated.

He surely cannot be entrusted with any significant public office again, but should be left to potter about, fairly harmlessly, with his silly 'faith' foundation. Like most prime ministers, he was much exercised about his 'legacy': it is as indelibly tainted by Iraq as Cameron's will be by Brexit. As well as hundreds of thousands of Iraqis, 179 UK soldiers died between 2003 and 2009. Relatives of the British dead attended Chilcot's presentation of his report. Apparently Blair had more pressing claims on his time.

Read more in the London Review of Books

Edward Said: The Academy of Lagado · 17 April 2003

David Runciman: The Politics of Good Intentions · 8 May 2003 Conor Gearty: The Hutton Report · 19 February 2004

Eliot Weinberger: What I Heard about Iraq · 3 February 2005