I haven't seen the video. The news reports were graphic enough.

Adding to the horror of the five men murdered was the boy, thought to be under 5, in military fatigues and a black bandanna bearing Isis markings declaring: "We will kill kuffar [non-believers]."

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It's depravity beneath depravity. But I find myself disturbingly inured and distant from it. I can't understand or process the barbarism.

Here we are, in the middle of a Kiwi summer and elsewhere in the world this is going on. The murders and the chilling message pop-up on my phone when I am at the park with other families revelling in the sun.

The horror is instantly brought to me through the juxtaposition of medieval barbarism and the wonder of modern technology. I gasp and go back to play with my children.

How can this be? I grew up with such hope for the world. Things were getting better. I imagined, thanks to John Lennon, a world with "nothing to kill or die for".

And the world is more prosperous, there is less starvation and poverty, we know more and we understand better. And then there's this.

The 20th century was wondrous - from horse and cart to man-on-the-moon and supercomputers in our pockets.

It was also the century of the worst of horrors. Mass starvation and the world engulfed in wars that did not distinguish civilians or soldiers, women or children.

But we learned, surely? The evil men were dealt to. Never, again, we declared. We have the United Nations.

And now it's the 21st century and the Age of Aquarius is upon us. Peace is guiding the planets and love is steering the stars.

But my phone has a video of five men being murdered and a small boy promising more.

Perhaps we shouldn't be surprised. Within the human heart is a primitive beast capable of death and destruction beyond any other animal.

The odd thing may be that we thought things were different. That something within us had changed. And all the while the tools that let us prosper also let us destroy.

The little boy's mother grew up in south London. Her father drives a taxi. Two years ago she left Britain for Syria to join the Isis terror group.

It's not just a mum who has done this. It's a group. And a frighteningly large and well-resourced one.

That poor boy serves as a grim reminder. We can sing of peace and love and wish for a better future. But all experience suggests we must always be prepared for the other.