Late in the summer of 1993, when I worked as a reporter on the Bookseller magazine, I was despatched to interview Iris Murdoch at her large, eccentrically dishevelled house in north Oxford. She had just published The Green Knight, her 25th novel, and I was amazed when my idle request for an interview was granted. As it turned out, it was to be one of the last she ever gave. Not four years away from being an undergraduate, I was gauche and clumsy in her presence, mumbling the word “Dame” several times when she opened the door and stumbling over books scattered across her narrow hallway. My first question, describing one of her characters as “imperiously innocent”, was greeted with a sympathetic smile and then a question of her own: “What exactly do you mean by that, young man?”

It was hard, listening to the tape of our conversation again this week, not to read into the gaps and omissions in her sentences - the stumbles and pauses, the memory lapses - early evidence of the Alzheimer’s disease that banished her, for the last 30 months of her life, to a twilight realm of memory loss and baffled wonder. That morning, her stomach gently rumbling, she spoke with powerful regret of what she saw as the hard secularism of the modern world. “I think people must make an effort to retain Christianity, but in a non-literal form, as it were - not having to believe in God as a person or that Christ was divine, but to believe in everything that Christ meant. This is something that mustn’t be lost . . . I believe it is quite possible to have a kind of teaching of religion which is not just meant for Christians. Some sort of teaching of morals should be present in schools. The problem with so many schools is that they remain under the influence of the free thinkers of 1968; they don’t bother about spelling and everyone is into free expression.”

Her fiction can be read as a kind of an extended elegy for that lost world of religious certainty of which she spoke, her characters stumbling unhappily in the spaces where God used to be. Her best novels are intricate moral parables, mini-quests on which her always educated creations embark to answer the question posed by Michael in The Bell: “What is the requirement of the good life?” A moral philosopher, Murdoch was genuinely troubled by this question, and she worried away at it, returning again and again to it, as she sought to refine and animate a secular morality. If her writing could be solemn, overdetermined and repetitive, it was also surprisingly sensual and hard to forget. Hard to forget because of its very strangeness and eerie rigour. She sounded like no other writer.

Murdoch famously never allowed her work to be edited. It began to show. As she grew older, her novels, particularly the sequence of five beginning with The Philosopher’s Pupil (1983) and ending in The Green Knight, became longer, more opaque and mannered: a great continuous symphony, with each work an instrument complementing and commenting on the one that went before. Late-phase Murdoch invariably featured a brilliant charismatic, a Wittgenstein-like figure who exerts a mesmeric hold over a group of people - Lucas or Peter in The Green Knight, Gerald Hernshaw in The Book and the Brotherhood, John Roberts in The Philosopher’s Pupil; the characters’ love relations are painfully intertwined; there are Shakespearean echoes; there is a mythic or visionary perspective; and death is always the intruder.

Peter Conradi, in his Guardian obituary this week, approvingly compared Murdoch to Dostoevsky. This is an important mistake. Murdoch may have grappled, like Dostoevsky, with moral and theological dilemmas, but there is none of the Russian’s urban mania in her fiction, little of his existential extremism or tortured interiority. Reading Dostoevsky you feel that anything might happen; that the author himself, like a racing driver pushing himself and his car to the limit, had no idea where his erratic talent might take him, or what form his novel would take. Murdoch, by contrast, knew absolutely everything about her characters and the form of her novel before she began writing. The hard work was in the thought and planning; there was little to surprise her in its execution. So hers was a controlling, almost divine literary intelligence.

Iris Murdoch’s own search for the good life was politically interesting; she metaphorically crossed the floor. Her journey from youthful illusion to disillusionment, from early support of the Communist Party to a kind of inchoate Thatcherism, was a model for her generation. By the time I met her a sad twilight had settled over her; she confessed to being “deeply disillusioned” by the contemporary world, by the cheapening of religion and the failure of progressive educational policies (she considered the comprehensive model a disastrous experiment in social engineering, more extreme than even the educational system of Soviet Russia).

“I became a Marxist at the time of the Spanish civil war: it was an emotional period as those who were against Franco were swept to the left,” she told me. “At that time, I read a lot of Lenin and was caught up with the notion of building a better world. But I became quickly disillusioned with Marxism; the ideals were OK but what was being done in its name was awful. I remained on the left for a long time, up until the emergence of Arthur Scargill, really. I don’t know where I am now - I feel very distressed by politics.”

As a young woman Murdoch met Sartre and was swayed by the radical self-liberation of existentialism; she moved on to embrace a kind of ethical Platonism through which to see the good is simply to see the world as it really is.

To the end, though, she was unable to make that final leap into faith: a theologian in search of a consoling eschatology. “God does not and cannot exist,” she wrote. “But what led us to conceive of him does exist and is constantly experienced and pictured. That is, as an Idea, and also incarnate in knowledge and work and love.”

She and John Bayley, her devoted husband of more than 40 years, had no television. “At intervals,” she told me, chuckling, “we get notes from the local authorities saying, ‘We see that you have no television set, what is the reason for this?’ and I have to reply, ‘We don’t like television’. I very much agree with Whitehouse and others that indiscriminate television can be very damaging to children, even the very jokey things.”

The sadness is that Iris Murdoch, in her last, levelling years of illness, came to like television very much indeed, particularly Teletubbies, which she would watch in a kind of rapture each morning, one of the best minds of her generation entranced by the overlit, technicolour simplicities of La-La, Dipsy, Tinky-Winky and Po.