THOMAS SUTCLIFFE: Steel yourself for a conversation

Walking round Tate Britain's Sir Anthony Caro retrospective I was struck by an obvious thought. Regrettably, this kind of collision is far more common than sudden impacts with the dazzlingly original or the conceptually unprecedented, but you have to work with what you get, don't you?

The thought was this: there are very good reasons why people are nervous of abstraction. I confess that I'd entered the gallery in a slightly timorous condition myself, knowing that my already chronic gallery-neurosis (is there anything more unnerving than a roomful of objects waiting for you to react?) was likely to be tweaked to an even higher level by Caro's wholehearted embrace of abstraction. Spirits were not high, I think it's fair to say - and I did wonder a little whether anyone would be going to the Caro with real excitement. Nostalgia, yes - if Caro was part of the your generation's set-dressing for modernity - or even scholarly interest, for younger art-lovers who might want to fill in a couple of blanks in their I-Spy Book of 20th Century Art. Respect too, perhaps, for those who recognise the seriousness of Caro's vocation and the quixotic heroism of making collages out of two-inch sheet steel. But thrill? Anticipation? I suspected not.

This wasn't because Caro is a forbidding artist in any obvious sense, because he isn't. The retrospective reminds you that he can be as vibrant a colourist as Bridget Riley - and any artist who can include the word "jewelescent" on the descriptive label for a piece can scarcely be accused of puritanism. It was because the work (after the traditional "false start" room, full of bulgy bodies doing mundane bodily things) wasn't representational.

With representational art - and the first room of the Caro show makes this point effectively - you can be absolutely certain that the object and you will have at least one shared interest: what things look like. Here's a blobby man taking his shirt off. He looks like no human on Earth, but that doesn't matter because it's clear that Caro is after some kind of amalgam of sensation and vision. He's tried to represent what it feels like to take a shirt off - if you've neglected to undo enough buttons and the shirt is bit tight. And since we can see immediately that this is what is going on we can, at the very least, make small talk with the sculpture in the hope that a deeper kind of conversation might emerge. The artist's perception and ours come together with an almost audible click - like a snap-fastener - and while this is just the beginning of what any halfway decent figurative art does, it is at least enough of a beginning to hold off awkward silences.

But consider a large assembly of pre-formed steel girders, tubing, I-beams and steel sheeting, all of it painted bright red. What has it got to say to us, or us to it? Can you think of an opening gambit? And what will fill the gap if you can't? Facing a work of uncompromising abstraction, the temptation to fill the silence with anything, even something stupid, is quite high, because the piece itself is usually provokingly mute. And this can easily feel like a kind of dumb insolence - a sullen refusal of the usual courtesies of introduction. It's up to you to make the first move, to ask the first question - and even when you have, the piece isn't going to let you know whether you're on the right track or not.

If this happened with a person it would leave you deeply unnerved - and, though our encounters with objects are obviously very different, there is some kind of perceptual leakage between meeting an unfamiliar thing and meeting an unfamiliar person. Even if the work is prepared to compromise it can be tricky.

The Caro sculpture I've just described is called Early One Morning, which is positively chatty by the standards of some abstract works (you know the kind of thing: Piece XIV, or Painting Five). Don't hope for the snap-fastener thing though, because it just won't happen. I know what feelings those words summon in me but it is virtually impossible to make them stick to Caro's sculpture. Press as hard as you want and you'll just end up with a sore thumb - or the kind of art-speak that the Tate's leaflet resorts to: "inner dynamism" and a sense of "immanent life".

That, I realised after a while, is what makes courage fail at the door so often. It's not really abstract art that's unnerving - it's the obligation to interpret it. If you can arrive at a point where you feel you can take or leave these objects - where you owe them nothing - you may be surprised by how often you find that you really have a lot in common. They're actually quite sociable when you get to know them.