A year on, ponders questions of faith brought out by the hauntings at Peterhouse.

I haven't been here long. And time counts. Peterhouse was founded in 1284. Its oldest buildings date from the 14th century and the dean occupies rooms in its oldest quarter - rooms that remain mysterious. For there is a corner by a window on the right, overlooking the Fellows' Garden, into which a half-hidden alcove is set, large enough for only a prie-dieu.

And more mysterious still is the three-by-eight-foot space cut from the room that appears on no map of the college buildings. What occupies this space between the dean's set and the small parlour no one can say. It remains a spatial question in the college's architecture and history.

So tales of hauntings, while not everyday, are easily accommodated. In my first few days as dean I sat in my room unpacking books, impressed by the Elizabethan panelling, the Delft tiling of the fireplace and the William Morris rug. It was an early January evening, dark and frosty. Term had not begun and I knew nothing about the college's past. There were the heavy footsteps of two or three people ascending the wooden staircase. The corridor door adjacent to my room swung open noisily. "No we can't go down there," a young voice said. "It's only for the fellows. And besides, it's haunted." The door swung back as the footsteps retreated.

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Let me say now that I have never seen the ghost of Francis Dawes, the 18th-century bursar who hanged himself, or the ghost of one of the college's Nobel prize-winners. But it is amazing what suddenly appears out of nowhere once it is rumoured that there is inexplicable knocking in the old Combination Room or strange manifestations of some sort. After the two sightings by college staff last year and the bursar's more elaborate encounter with a phantom, journalists and exorcists popped up everywhere.

The telephone rang for days with requests for live radio debates and filmed interviews. Letters arrived from all over the world. I lost count of the number of white witches, druids, fakirs and mediums who offered to exorcise the spirit, suggested they were already telepathically in touch with it or advised me to leave it alone. I passed on to the bursar requests from spiritualists and researchers of psychic phenomenon to spend a night in the Combination Room. And other Peterhouse tales began to appear: a woman wrote to say that her now deceased husband had spoken of paranormal encounters he had had as an undergraduate; accounts of two exorcisms that had been performed in the recent past; and verbal reports from ex-students of their own supernatural encounters.

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Recent rumours of more ghostly turbulence should not have come as a surprise. Of the fellow who is reported to have told The Times that a new dean was being brought in to deal with the exorcism of Francis Dawes's querulous spirit by a public ceremony to be performed in the Old Hall, nothing is to be seen. No one is admitting having spoken. The dean-elect has heard nothing of the matter. No, there have been no nocturnal knockings, no late night tete a tetes between the bursar and the spectre over the taking of an apple, no sightings whatsoever since last October. So was it exorcised after all?

My problem, when faced with the possibility of performing an exorcism, is what it is I believe I am doing. Am I presiding at a requiem mass for a tortured soul trapped into constantly reliving an event that keeps him or her bound to this earth? Or am I conducting a rite to help certain members of a congregation, or college in this case, negotiate a traumatic and inexplicable event? In brief, am I exorcising something otherworldly or exorcising the fears of those living and working in buildings where something uncanny has occurred? The answer to that question, even if I am doing both, depends on what I believe about ghosts. Are they real or are they projections of a psychic disturbance in those to whom they manifest themselves?

They do not teach you an answer to those kind of questions in theological college. In fact, systematic Christian theology is embarrassingly silent on the matter of ghosts. There are reasons for this. Contemporary Christian theology of the conservative postmodern or the radically orthodox variety eschews dualisms of the soul and body sort. The received wisdom about ghosts is that they are eternal souls wandering, on the other side of death, free from their bodies. So the theological difficulties with ghosts become evident. Post mortem, Christ, as represented in his resurrection appearances, remains embodied, not free-floating ectoplasm. Now the resurrected body of Jesus Christ suggests that the material order does not conform to scientific positivism or medical materialism. Creation is shot through with the watermark of the glory of God. Hence things unseen, like angels, and things seemingly prodigious, such as the miracles of the virgin birth or the raising of Lazarus, can be accommodated within a material order created, saturated and sustained by grace. So it is not that theologians dismiss the mysterious and inexplicable in the natural. Natural phenomena always retain a divine mystery about their identity. But ghosts - detached, ethereal, grief-stricken souls - do not find an easy place in this Christian theological account of the creation.

Ghosts raise a question that clearly distinguishes between a theologian and a teacher of Christianity as a world faith. When I came across the two college staff who had been appallingly frightened by what they had witnessed in the Combination Room, I found, as a Christian theologian, that their experience raised questions about the Christian faith and my understanding of that faith. And how I understood the experience of those two men in terms of the practice of my Christian faith determined whether I could perform an exorcism and how I understood what it was that was taking place within that exorcism.

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Theology is the ongoing work of understanding the world and what is given to each of us as experiences within that world in terms of a faith already held. In this it is distinct from Christian studies, which is an intellectual endeavour with respect to a specific body of knowledge. Theology is a practice, reflecting the living out of what is held by faith - a practice that engages the whole of one's belief systems. Furthermore, to participate in that ongoing questioning and understanding of the faith, is the working out of one's own vocation, one's own salvation, a drawing closer to God and a presentation of the world back to God in order that its redemption might be understood and furthered. If I were not a believer then there could be no understanding, no pedagogy important for salvation. And in performing the exorcism I would not have known what I was doing or I would have performed an office and a rite of merely social/psychological significance. Being a theologian, whether Christian, Jewish, Islamic or other, is a vocation, not a job. Some of us are able to make it our job, but all practitioners of a religious faith are theologians to the extent of being called upon to interpret the world in terms of what they believe and shape their lives in accordance with the virtues enjoined by that belief.

So was the ghost at Peterhouse exorcised? No. The phenomena reported by the three people last year and the memories of past undergraduates was too eclectic - a presence here, a shape there, a figure in period costume, knocking in the wainscoting. Furthermore, as I have said, all is now quiet in the precincts of Peterhouse as attention turns to matters more academic and economic. No doubt in a college rich with historical association, where, in the candlelight, the shadows crush together in the corners of panelled rooms, time, space and knowledge will once more fold. In a world where secularism is imploding and an X Files paranoia about what is really "out there" dominates the popular imagination, the mysterious and the inexplicable will once more surface. Theology, Christian theology anyway, does not give us the solutions to these enigmas. But it is only within the realms of the theological that an understanding can be sought.

Graham Ward is the former dean of Peterhouse, Cambridge. He is now professor of contextual theology and ethics at Manchester University. Religious studies books, pages 26-29.