We can't stop this.  Sorry, but we can't.  As we ruminate on a thousand hows and what ifs – such as how the hell did someone like Man Haron Monis find himself out on bail – there's a brutal truth we can't escape: we're trying to impose order on chaos; to convince ourselves that everything can some day be under our control, when it just can't.  Tony Abbott deserves lasting admiration for having the courage to admit as much.

From all appearances, this was as crude and as solitary as it gets.  There's no high-tech wizardry on show.  There's no elaborate, maniacal plan worthy of a Hollywood supervillain.  There's not even a mastermind pulling strings to make this more coherent.  There is only a man, a gun and a flag.  The man and the gun we've seen before.  Indeed, we've seen it horrifically often: in Belgium just hours after Martin Place; at Port Arthur.  But the flag – that changes things.  It lends this the apocalyptic timbre that drives us so mad.  It's the thing in this episode that does the least damage – and the most.

It's also the thing that makes this global.  There's every reason to suspect we're dealing with someone deranged here but many deranged gunmen have gone before him.  Only rarely do they associate themselves with the symbolic power of a global militant movement.  At no point in the history of our species have such human satellites, living beyond the margins of even the most marginal groups, had the power to do so: the power to become so much more than they are simply by attaching themselves to a symbol from another continent.  And right now, there is no symbol more potent and available than that of Islamic terrorism.

So, Michael Zehaf-Bibeau and Martin Rouleau Couture in Canada.  Zale Thompson in New York.  Now Monis at Martin Place.  We're seeing this more now: troubled (often criminal) histories, possible mental illness, religious conversion, violence.  Monis apparently converted to Sunni Islam only recently, perhaps because you can't really claim to love IS when you're a Shiite and they're trying to exterminate you.  Islam has such permeable borders, such an absence of hierarchy, that anyone can become anything in their own mind.  Its symbols are available to anyone who wants to claim them and there is nothing anyone can do to stop them.  Australian Muslims had been disowning Monis for at least seven years.  They'd even expressed their concerns to the authorities.  But how can you stop the "fake sheikh" being real to himself?

There's no control order regime to account for this.  There's no metadata inside an apparently deranged mind.  We're busy fretting about the terrorists' tools of the future – which is all fair enough – while they wreak havoc with the tools of the past.  Think about what we've seen lately, from Australia to North America: a knife, an axe, a couple of guns, even a car.  Perhaps the most profound aspect of our age is that the power to inflict carnage is now shared with the small to the invisible to the otherwise insignificant.  Man Haron Monis was so insignificant, hardly anyone knew him; so insignificant the system overlooked him.  And now he's history.

But there's another history to be written here.  One that is very much in control.  It's a history written not just in the statements of leaders, but in the minutiae of our everyday interactions.  It's the history we glimpsed as the siege unfolded when a single, humble Australian decided to declare #illridewithyou in solidarity with Muslims too scared to ride public transport.  It's a history that commenced with the interfaith vigil held at the Lakemba and Auburn mosques.  And it's a history to be determined by what we decide this tragedy symbolises: the sordid ideology of a man who deserves to be forgotten or the greatest virtues of those of us left behind.

Waleed Aly is a  Fairfax columnist and hosts Drive on Radio National.

SMH