IN THIS TENDER but tough work of art, coming out in the author's 73rd year. Paul Horgan tells us his mind on love and lust, mercy and moral erosion. It is his declaration of humane alternatives: Feel, think change.

The perspective is strange. A 70-year-old man of sensibility passion this biography corresponds to Paul Horgan's locks back on his life at 20. As he tells his story of love and death, he senses that the moral design of everything ahead seemed to be forecast in the upheavals, breakdowns and sensual tides that engulfed his mother and father while much of the United States was rocking to sleep with Calvin Coolidge.

We've met Richard, the narrator, at earlier ages in two previous Horgan Novels, Things As They Are (1964) and Everything to Live For (1980). If they were about the loss of innocence. The Than Mountain Air confirms the cost of that loss and extends its possibilities. Adultery, murder, and political crime are perversions of sex, rage,and aggrandzement.

Richard leaves college in the spring of around 1923 to help his father campaign for lieutenant governor of New York on a Democratic ticket headed by a florid judge once indicted for bribery. His father wears responsibility as if by divine right. He carries the election. Shortly after inauguartion Richards father clooapses with a tubercular hemorrhage. Richard and his parents leave their Henry James mansion in Dorchester, which looks like horgan's native Buffalo, for a sanitarium in Albuquerque and a society much sicker than anyone in a hospital.

Appearances continually split from reality in The Thin Mountain Air. The elegant, phlegmy society of Anglo-tu-berculars in Albuquerque contains deceits and bigots whose empathy for one another is as frail as theirunderstanding of the Spanish-Mexican-Americans whose space they usurp. Richard's father draws information from a network of agents in the New York senate to nourish his fantasy of succeeding the corrupt governor who must be evicted from the state house. Richard himself, puzzled witness to "corruption...everywhere" and the "differences between visible style and invisible character," is drawn into a charade of love and a stupid murder for sex that becomes the dramatic center of the novel.

Richard too begins showing signs of T.B. and is sent by his father's physician for a month of toughening up on a sheep ranch owned by an ancient patrician. Don Elizario Wenzel has taken as his wife a beautiful girl 55 years his junior. She is angelic property, a statue to clother in silk, and respectability to guard by night. It is only a matter of time before one of the shiip-dipper ranch hands tries to give Concha what Don Elizario barely remembers.

Handsome as a stud horse, radiating energy, Buz Rennison "shed good will with smiling indifference." The women of the world await him, and he is always ready, as he shows Richard during a weekend orgy in town. "Most offensive of all, he was like an allegory of all-knowing innocence in the midst of ignorant experience." Concha denies Buz's simple ginad universe. She loses, and Don Elizario dies in a trough of sheep dip. The catastrophe moves Richard further toward maturity: "I came home from a land which gave space to my vision, and loss to my youthful conviction that virtue controlled all. Now I knew that virtue had to be salvaged as best it could out of every human stiuation. The sacred and the the profane had previously been separated for me. Now they had bllurred edges . . ."