The trip became a boozy, low-life parody of the Georgian milord's Grand Tour, taking in the taverns of Gravesend and Rochester instead of the art galleries of Florence and Rome. The friends engaged in a variety of rowdy activities, and it was noted that Hogarth showed particular skill (appropriate to a satirist) in the art of flinging dung.
Hogarth's unruliness remains his most endearing characteristic, partly because it was unruliness of such an innocent kind - a childless man, he remained something of a child himself long into adulthood - and partly because it suggests a secret sympathy between the satirist and his targets. The idea that Hogarth regarded erring humanity with a kind of complicit benevolence lies behind a popular but sentimental view of his satirical art - namely, the belief that his moralising savagery masked more humane instincts, above all a desire to celebrate life in all its rich diversity. There may be a grain of truth in this but to see Hogarth's art as essentially life-affirming softens him too much.
The titles of Hogarth's best-known works, the Rake's and Harlot's "Progresses" were borrowed from John Bunyan's Nonconformist Christian allegory The Pilgrim's Progress. But where, in Bunyan, the pilgrimage leads upwards to God, Hogarth's characters only ever proceed down, towards the pit and damnation. Duped by inappropriate ambitions, deluded about their place in life - the Harlot dreams of wealth and respectability, while the Rake apes the lifestyle of a wealthy aristocrat - their lives are object lessons in the stupidity and sinfulness of harbouring unrealistic aspirations.
There was an element of sadism here, an unwillingness on the part of the artist to allow his creations the worldly success which he himself had enjoyed. Hogarth's Progress, in which he rose from being the son of an impoverished schoolteacher, to become the son-in-law of a knight of the realm and, eventually, Serjeant-Painter to the King, was itself a counter-argument to the doomy inevitability of his best-selling prints. His life showed just how far an ambitious person could rise in the unprecedentedly fluid social world of 18th-century London.
He was born near Smithfield Market, which was transformed each November by Bartholomew Fair. Hogarth seems to have spent a lot of time visiting the booths of the fairground, where hack actors and actresses performed theatrical entertainments of greatly varying quality; and much later in life he wrote that "shews of all sort gave me uncommon pleasure when an infant". Then, when Hogarth was 10, the Latin-speaking coffee-house which his father had opened, in the naive hope of making his fortune, failed and the family went bankrupt. Hogarth's mother was reduced to hawking patent medicines and his father was confined to the debtor's prison, the Fleet, for several years.
The memory of "shews" and the Fleet, theatre and the spectre of prison, would recur constantly in Hogarth's work. The two themes are explicitly linked in one of his earliest paintings, in which he depicted a prison scene as played in the theatre (which he had seen in John Gay's Beggar's Opera) and they are implicitly linked in much of his other work, above all in the Progresses. In the preface to his novel Joseph Andrew, Henry Fielding wrote in praise of Hogarth that his figures do not only seem to breathe "but to think". In fact, they look even more as if they are acting, as if the painter had imagined not life itself but life as it is played in the theatre. Hogarth's vaunted "realism" is almost always on the edge of slapstick or melodrama. The Rake, vainly shaking his fist at the fates in Bedlam, is clearly not a real lunatic but a stage madman. Hogarth's interiors (and most of his scenes are set indoors) often look like stage sets. This is not necessarily a failing, theatre being an appropriate metaphor for his black view of life itself as a kind of theatrical imposture, each person acting the person they would like to be, trapped by an unrealisable fantasy. In this sense, theatre and prison became the same place.
Hogarth's own unrealisable fantasy was the dream that he might one day be recognised as a history painter: a painter of high rather than low subjects, a master of the sublime instead of the ridiculous. It was a dream he conceived as a young man, when he went to see Sir James Thornhill's enormous, if somewhat grandiose, painting on the ceiling of Greenwich Naval Hospital - then the most ambitious exercise in narrative art ever carried out by an Englishman.
The desire to create something to rival it stayed with Hogarth throughout his life. It prompted him, once he had started his own business as an engraver, to broaden his horizons by enrolling in Thornhill's art academy, where he first learned to paint; and it must have had at least something to do with his decision to pursue and marry Thornhill's daughter, Jane, thus making the artist whom he wished above all others to emulate into, so to speak, his father.
It was evident to everyone except Hogarth that he was temperamentally incapable of painting solemn narrative works. His efforts in this genre amount to a gallery of almost unknown Hogarths: The Pool of Bethesda and The Good Samaritan, for St Bartholomew's Hospital; Moses Brought Before Cleopatra, for the Foundling Hospital; and Sigismunda, his last painting in the tragic vein, which so disgusted Lord Grosvenor, who commissioned it, that he told the artist he could not bear to keep it in his house.
This last episode seems almost to have broken Hogarth's spirit, plunging him into illness and depression for more than a year; the final disappointment of his ambition to be taken seriously, it accounts for the unrelieved bleakness of those late prints, The Cockpit and The Bathos. In these works, the expression of his final disenchantment, both with himself and the world, Hogarth did actually achieve something like the grandeur he dreamed of creating in his histories - a new form of satire so extreme it has turned into something else, a negative sublime that anticipates the brilliant, troubled graphic work of Goya.
Hogarth's greatest gift was his ability to mimic and mock the established genres and conventions of art - to subvert them from within and to produce, as a result, something entirely his own. This is evidently true of the Progresses, which are deliberate low-life parodies of high narrative art. This same spirit of parody hovers behind everything that Hogarth ever touched, as if the spirit of subversiveness was so strong in him that he couldn't resist falling into pastiche even when it was not quite appropriate. It explains the disastrous weakness of his history paintings - despite himself, Hogarth has made them look mock-serious, his Cleopatra a fishwife, his Saint Paul a London streetcrier.
Something similar, albeit in a less obvious form, also accounts for Hogarth's tremendous originality as a painter of portraits - the most underrated aspect of his oeuvre. There is something unruly even in his quietest group portraits, like the wonderful Graham Children - where the mannequin stillness of that most stultifying form of Georgian painting, the conversation piece, has been disrupted by a powerful, turbulent sense of life. While the children smile and play, the cat is about to kill the goldfinch in its cage. This mood of perpetual unquietness is perhaps the most quintessentially Hogarthian aspect of Hogarth's art.
One of the saddest aspects of his career is the fact that he himself seems to have considered his most original invention, the "Modern Moral Subject", as he called the "Progresses" and Marriage a la Mode, as a bit of a music-hall turn designed to exploit a new-found middle-class market; a debased form of the grand narrative era that he really wanted to practice. He was, in many ways, a man divided against himself, and there were several other aspects of Hogarth's art which Hogarth himself did not fully value. He was capable of extreme sensuality, as the Shrimp Girl, perhaps the most popular of his works, more than adequately proves - but she represents almost the only passage of entirely unmoralised and unjustified beauty he ever allowed himself to paint. It is as if Hogarth, who started his life as an engraver, distrusted his own abilities, as a painter, to create such beautiful phantoms - the puritanical side of his nature hated the idea of art that was merely lovely, rather then useful.
The most important part of his legacy lay not, perhaps, in any specific aspect of his oeuvre, whether as painter or printmaker, but in what he was. In Britain, until the mid-18th century, nearly every artist had been resigned if not reconciled to the role of a rich man's hireling. But Hogarth was one of the first British artists to earn his own living in his own way, to form a career independent of the patronage of the wealthy. His moral example was of incalculable importance to the generations of artists who came immediately after him. Looking at the most famous of his self- portraits, the Tate's Self-Portrait with Pug, we see that a new spirit entered art in Britain with the arrival of Hogarth - a new pride, a new sense of what an artist might amount to and, indeed, of what art itself might be.
When Hogarth died, he was writing his autobiography. He never finished it, but he did complete the dedication. It sums up his truculent, determined spirit of independence. He called it "The No Dedication" and it may stand as his epitaph:
"Not dedicated to any Prince in Christendom for fear it might be thought a Bold piece of arrogance.
Not dedicated to any man of quality for fear it might be thought too affecting.
Not dedicated to any learned body
of either of the universities, or the
Royal Society, for fear it
might be thought
An uncommon piece of vanity.
Nor dedicated to any particular friend
for fear of offending another.
Therefore dedicated to nobody
But if for once we may suppose
Nobody to be everybody as everybody
Is often found to be nobody,
then is this work
Dedicated to anybody
By their most humble
and devoted, W. Hogarth."
`Hogarth the Painter' opens tomorrow at the Tate Gallery, London, SW1 (0171-887 8000), to 8 June; Andrew Graham-Dixon is presenting BBC2's tercentenary tribute to William Hogarth, due to be screened in April