"an unresolved mass of imagery, which sort of in the end... floats over people"

That's what you get if you say, when taking the picture, "let us for the umpteenth time capture the pathos of a starving child" - and not, "why is this child starving?" "Who's denying the food? What's the background, what's the history?"

So says the Magnum photographer Philip Jones Griffiths, who died yesterday aged 72. A Welshman who left Wales at 16, but said that growing up there influenced everything he ever did, he spent a lifetime photographing conflict and its aftermath so you wouldn't have to.

Of his work in Vietnam, photographing the effects of the war on civilians, he said to the BBC in 2005, "I wanted to show that the Vietnamese were people the Americans should be emulating rather than destroying." He was instrumental in influencing American opinion against the war.

But it wasn't all war. His photographs from Wales and England from, being frank, before Ms B was even born (this is somehow humbling, when you go to look again) are starkly revealing - of things Britain probably didn't want to know.

He says, "Any intelligent society would somehow give special privilege to critics. It's by criticising society that humanity has made progress... However, that's not the way the world works right now. What you have now is that you have the bandits in control, and they control the way people think." Follows a detailed explanation of how the bandits do this. All on film. Beautiful. Listen to him - listen to him on the visual history of the 20th century - and learn.

While he will be right in what he says about power and control, he also has a point about the power - and the responsibility - of the photographer. This man helped to make the very history that was being written while I was growing up. We say these images are "iconic," but that's just lazy. Think about what it means to be the person who made something so powerful and important. Jones Griffiths lies somewhere behind all of little Miss B's backyard ruminations on the nature of war, the world and her place in it as a little girl and future woman, whether there would still be a draft when she reached 18 and whether they would be drafting girls by then, what she would do if they were, America's place in the world, what it would be like to be a little Vietnamese child, etc. That's the power these images had.

I think he'd be happy to know about those ruminations. This is photography with a heart - with empathy, encouraging empathy in its viewers - but above all it's photography with a mind, in service of truth, against cant and self-serving conveniences. Jones Griffiths wants you to feel, but even more than that he then wants you to think.

Don't get me wrong: Ms B loves art for art's sake. Indeed I have argued its case many's the time; but the success of the case may depend on what is meant by "art" and what, at bottom, one thinks it is for (even when only in its own service). Jones Griffiths understood about art. He said, I forget where, something wonderful about the first time he ever saw a photograph by Cartier-Bresson (aka, of course, the Master). It was upside-down. He was in a class or something, and the teacher had deliberately reversed the picture so as to draw attention, not to the subject, but to the composition. Jones Griffiths said this had a permanent effect on how he looked at things, and this to me is a sign of the utter integrity of his vision. An eye that can't push itself past the obvious and really see what's there is no eye. And a heart and a mind without an eye cannot produce art - and photo-journalism, without being art, cannot succeed.

Some people might say 72 was a good age, but to lose this person now, at a time when we need his particular qualities so much, seems a tragedy. He was so young. Younger than we are.