Howard Jacobson: A sense of tranquillity is the last thing you can expect to find in a Florentine piazza

Americans in Huck Finn pants enter the square in robotic reverence to work which is the fruit of greed

Caro Lettore, Cara Lettrice,

Dear Reader, anyway, I am writing to you from the Piazza della Signoria in Florence, that astonishing outdoor theatre of expostulating bronze and marble where Stendhal felt his knees buckle and Lucy Honeychurch, heroine of A Room with a View, saw one Italian casually knife another. It's a memorable passage, the dying man opening his mouth, "as if he had an important message for her", but only a stream of red issuing from his lips.

It's a touch quieter than that in the piazza as I write, though my knees did buckle when I saw the statuary again, and last night I watched from my hotel window as two rival groups of pedlars – sellers of reproductions of soft-focus boudoir nudes – fell out over something or other (it might have been money, it might have been aesthetics) and tried settling their differences with their fists. No one was murdered, but it did take 20 bella figura Italian cops to separate them, and in the morning there were blood stains on the cobblestones. So art and violence still make fine accommodations with each other here, as is appropriate when most of what the art commemorates is brute power, decapitation and rape.

I'm here to find calm, having just finished a novel but feeling it should settle before I present it to the world. Some books need to air more than others when you've finished them, and this one's been brewing in the deepest dark. The idea is that if I spend a week looking at paintings and sculptures, I will forget about words for a while. And I am one of those people for whom a holiday from words is necessary if I am to enjoy any sort of tranquillity. The trouble is I also need a holiday from vexation and Florence isn't quite providing me with that.

It's not the Stendhalian knee-buckling I mind. If anything I'd welcome more of it. But I can't get to see all the art I want to see because there are too many people here wanting to see it too. Does one tourist have the right to look down on others? That question is part of what's causing me vexation.

I'm not in a group, trailing behind a person holding up a green umbrella – that surely gives me some right of condescension. And I don't come straight from looking at the Titians in the Uffizi to buying a pair of boxer shorts with Michelangelo's David's penis reproduced on the fly, or one of those soft-focus boudoir nudes over which the pedlars fought last night – and that too must entitle me to a degree of art-tourist to art-tourist hauteur. No point going into the Uffizi, I say, if you're going to buy the same old crap you can pick up in Leicester Square the minute you come out.

But the real trouble is I can't get into the Uffizi. My hotel has sold me documentation which will get me past the queue which today extends half way to Pisa; but in order to turn the documentation into tickets I still have to queue, and even when I have the tickets I have to queue again to present them. So that's two queues (not counting the queue at the hotel) to beat the queue, whereas had I not tried to beat the queue I would only have queued once.

So I decide not to queue at all. Bugger the art. I will sit and write to you instead – caro lettore, cara lettrice. "The Piazza Signoria is too stony to be brilliant," E M Forster wrote, but to my eye it is brilliant by very virtue of its stony loquacity and harshness. It is a heroic place, allowing that the heroic neither comforts nor consoles.

And a paradoxical place, too – an unending crocodile of peaceably silver-headed Americans in Huck Finn pants entering the square in robotic reverence to work which is the fruit of ambition, greed and vainglory. But a paradox it should be. Art otherwise makes no sense.

So what's a critic as good as Professor Terry Eagleton doing trying to iron out its paradoxes? I disturb the piazza's roar to ask the question because of something I'm reading in the English papers. Never a good idea to read the English papers in Italy if it's tranquillity you're after, but maybe I only think it's tranquillity I'm after. Maybe what I really want is to see a stabbing, and to have someone deliver me a seemingly important message in blood.

Eagleton, anyway, is in the newspapers because of an attack he's just launched on Amis père et fils, accusing the former of being "a racist, anti-Semitic boor, a drink-sodden, self-hating reviler of women, gays and liberals", and suggesting that the last is in danger of heading in the same direction. Assassino!

I order another cappuccino and take out my notebook.

In general and wherever I happen to be, I have trouble with character assassinations of this sort, not because I abhor the violence, but because the failings in question are none of one's business in so far as they describe the man, and even less of one's business in so far as they describe the writer.

Racism, unless one actually catches the racist brandishing a whip, is usually in the eye of the beholder; boorishness requires a context, allowing that we are all sometimes boorish to somebody; self-hatred is all but de rigueur in a writer (why otherwise would one write), and as for reviling Jews, gays, liberals and women, what else do we look to a satiric novelist to do in times when Jews, gays, liberals and women are protected species?

With regard to the charge of drink-sodden – as a fellow writer and one-time academic myself, I scarce know where to look. Show me the writer who isn't, I say. Indeed, show me the professor.

Few critics read a text better than Terry Eagleton, but he's a Marxist – not some of the time, but all of the time, and you can't be anything all of the time when it comes to art. Come and sit in the Piazza della Signoria, where heads roll and satyrs leers and Sabine women are raped and raped again for our delectation, if you don't agree with me.

We play at reverence in these art-hallowed places, but we are fools to think that the art which we revere reveres us back. "As though art or those who make it were ever answerable to the liberal proprieties," I turn to say to my companion. But she's gone to take a closer look at Perseus lopping off the head of the Medusa, sculpted by that murdering lout, Benvenuto Cellini.