HENRY AND CATO is not a startling new development in the work if Iris Murdoch - her essentially 19th-century way of writing and working has an even temper that renders revolution unnecessary. The novel is rather a consolidation, another star for her literary firmament. Like Anthony Trollope of whom she is in some ways reminiscent, whe writes with frightening regularity in what she describes as "a completely business-like way," producing a notable novel almost every year.

Her new book is about two childhood friends, who have drifted far apart, coming to wrenching turning points in their lives. The corner, the sudden turn is a key device in Murdoch's novels to give her characters a hint of what lies behind them and a glimpse of the road ahead. Henry Marshalson and Cato Forbes are no longer young and both face a crisis. For Henry, the death of his hated elder brother precipitates him from peaceful, self-elected exile at a small mid-Western college, to being lord of the manor at Laxlinden Hall. Cato, meanwhile has become a Roman Catholic priest. As Henry flies back to England to assume his new role, Cato faces alone in a decaying London mission house a shattering challenge to his religious calling. His passion for God the Son has been supplanted by his consuming, so far platonic love for Beautiful Joe, the young tough with the shining hair and hexagonal glasses.

In different and diffuse ways both men fail to ride their crises. Both return home to be greeted as prodigal sons, Henry to his scheming unloving mother, and Cato to his domineering insensitive father. The interweaving of the parallel stories is endless and fascinating and it is a measure of Murdoch's superb craft that the effect, like that of classical ballet, is one of effortless grace, the labor and the discipline quite hidden. Henry has a widowed mother, Cato a widowed father, Henry a brother, Cato a sister, Henry rejects his inheritance, Cato his religious faith, a self-styled tart who is actually a typist; Cato lusts for a son of the slums, a small-time Irish crook. The symmetry is part of the complex pattern, yet is never strained or artificial. "The only writer I am sure has influenced me is Henry James," Murdoch has said. "He's a pattern man too."

Cato's failure to repel the assault on his priesthood leads to violence and death. It also sets the stage for some brilliantly executed cerebral discoureses between Cato and Brendan, his fellow priest and spiritual mentor, that lay bare the bones of faith and the loss of faith.

The strong religious theme in Henry and Cato brings us inevitably to the question of Murdoch and the philosophical novel. She seems to construe the description as pejorative and has herself criticized the novels of Jean Paul Sartre for being deadened by the weight of the message they carry. Her novels do not, in fact, stand or fail on their philosophy. They are built on the strenth of their characterization and this is especially true of Henry and Cato - the acute and sympathetic portrayal of Lucius Lamb, the aging literary hanger-on at Laxlinden Hall is an outstanding example - but the meat of these characters is their approach to abstract issues and moral decisions, surely the very stuff of philosophy.

Henry decides to divest himself of his riches and his ancestral home because he feels abstractly uncomfortable with the inequities of society. But his thinking is inextricably muddled and distorted by his life-long resentment of his late brother and by his desire for revenge on his mother who denied him her love. He is muddled and ends up - almost too schematically - with a devoted young wife "of good family" about to bear an heir to the heritage he attempted to destroy.

Cato's crisis of conscience is even more abstract, although graphically symbolized in the violence of his kidnapping and ransoming by Beautiful Joe. His attempt to escape into the shelter of the priesthood, to place himself beyond the reach of his exigent father fails, as did Henry's attempt to escape his inheritance. For Cato the results are harsh: driven back to the paternal home with apostasy on his conscience and blood on his hands, he has only a personal hell to contemplate.

THe philosophical content of the novel, like its intricate patterns, blends into the whole. On rare occasions, when the blending is not complete, there are slight flaws of omission and some unrounded characters. The scene is not set carefully enough for the happily-ever-after ending for Henry and Colette, Cato's sister. To make Henry's failure significant, his destiny should be more believable. Cato's protege, Beautiful Joe, is almost a caricature of the beautiful body and the rotten soul. It is hard to get any real sense of his deprived background or of the underworld that has molded him. Murdoch, who feels he is an important character, both admits and regrets his inadequacy. "I didn't quite know what Joe was like," she told an interviewer. "I feel if I could have made him a more sympathetic character without being in any way sentimental about him, it might have been a better book."

But fine writers are notoriously perfectionist. Despite the author's reservations, Henry and Cato succeeds in both entertaining and in contributing to our understanding of the muddles of mankind. It is a substantial and satisfying book.