The Anglican cathedral in the heart of Christchurch has become a forlorn, desolate tomb; felled by a destructive double-act of God. The massive earthquake of 4 September was the first blow which no doubt weakened it; the killer blow came in the form of the latest quake. At the time of writing no one knows exactly how many are buried beneath its fallen bell tower and spire. But already there are the triumphant proclamations from the city mayor, Bob Parker, and the dean of the cathedral, Peter Beck, that it should be, and will be, rebuilt and restored to its former glory.

And yes, a glorious building it has been, standing out as a rare architectural jewel of native stone and timber. We need all the beautiful buildings we can get in my native country of New Zealand – a country known as "GodZone" because of its majestic rural scenery rather than its generally functional but ugly urban dwellings. The cathedral was designed by Sir George Gilbert Scott, the British architect also responsible for St Pancras railway station in London. It was part of the original vision to create a lovely English city in the new country. And those Victorian pioneers succeeded, Christchurch being known as the "garden city".

But a great weakness has been horribly exposed. Brick and stone buildings become lethal killers in an earthquake zone. My feeling is that, despite our need for national optimism, a stone building in Christchurch can never again be regarded as safe.

Instead, once the deceased are recovered and respectfully buried, the cathedral should be permanently fenced off, with a suitable memorial plaque attached, and left as it is. Let it stand there as a ruined memorial to the dead. The cathedral has for me, become a monument to failure – God's failure to protect us from his own acts.

I'm still in a melancholic state of shock and feeling rather cynical not just about God – whose existence I doubt – but at the prospect of the remembrance services Beck and others will shortly conduct in his name. Of course, many will find comfort in these services which is good, but I won't be among them.

What will they say, these religious leaders? What can they say? For me, any thought of God rescuing some people became utterly untenable when the first named victims were two little boys aged 5 months and 9 months. And if they take the line that God suffers with us; well that notion also loses credibility when it is an act of God we are discussing here, not an act of war. The cathedral was not destroyed by a guided missile or suicide bomber. It was God himself apparently destroying his own house.

But, in addition to God's failure, a broken cathedral is also a symbol and monument to human failure. Questions may be raised in due course as to why tourists were allowed to climb a probably weakened bell tower and spire. But that is for later. Let me just make the general point here that humanists of all types, believers and non-believers, also need reminding of our human weakness. Let a ruined building speak to us all of technology's limits; that sometimes we are powerless in the face of nature's fury, and that when it comes to some aspects of human knowledge (such as seismology and prediction of earthquakes) we are still, to a large extent, operating in the dark. (The word "Titanic" also springs to mind.)

For our frailties, weakness and suffering, ruthlessly exposed in the face of powerful "acts of God" such as this has been, cannot be helped or removed by theological arguments about God's existence or vindication of his acts (theodicy). No, these things are intrinsic to our humanity; a burden all of us bear whatever our beliefs, and therefore in the end the only worthwhile question becomes: What am I willing to do about it; not as an atheist, Buddhist or Christian, but as a human being? What, in my small corner, can I do to alleviate the burden of suffering?

My good friend Donella emailed me the following insightful words:

Life sure is a curious and often painful existence. And I suspect that you are a bit like me, in that the older you get and the more you see, the certitudes of youth get shattered and torn and you stand still and silently like an old oak tree that has seen it all and carried on living anyway.

That ruined cathedral is like an old oak tree. It has provided shelter and beauty, and witnessed much joy and sorrow over the last 150 odd years. It is time to let it rest in peace, a witness to failure, both divine and human.

An axe has felled it, and whether it is an "axe of God" or merely natural, it is much more powerful than us. Let the tree lie.