Many, no doubt, will be familiar with Afroman's comic rap Because I Got High, in which good intentions - "I was going clean my room", "I would have paid my child support" - are derailed "because I got high". Particularly shocking for those reading these pages is the lyric "I was going to go to class ... I could have cheated and I could have passed" as an example of good behaviour foolishly forsaken.

Afroman is not alone in finding cheating normal. Once I was second examiner for a course in another department, and found myself faced with the task of giving a grade for an essay copied from a book I had written a few years before. Even more galling, the first examiner had given it B+. Later she kindly explained that she knew that the essay was derivative; she just hadn't quite realised how much so.

For the same course there was another essay so suspicious that I couldn't bear to read on after the first page. When I asked her opinion about it, my fellow examiner asked me whether I thought it had been written by that sweet old chap who comes and sits at the back in class. When I asked her why she thought that, she pointed to a page where the author referred to an argument he had first given in what he described as "author, 1965". The real author, of course, was a very distinguished scholar, and in the most naive plagiarism I have seen, this student had simply downloaded the paper in its entirety, clearly not even reading it before handing it in.

When academics hear stories of plagiarism we go through several stages, perhaps more commonly associated with being diagnosed with a fatal illness: outrage; frenetic activity; resignation. Our first reaction is always "hang, draw and quarter". Next comes the need to document the case, finding all original sources, comparing the texts, marker pen in hand, and working out what proportion is plagiarised, and then fill in numerous forms. A particularly tricky case can take a whole day - and a day in the middle of the examining period with a hundred more essays sitting on one's desk. But then, eventually, the student is confronted, and we are told a tale of boxes getting jumbled in a house move, notes losing their cover sheets, perhaps family problems leading to panic and disorientation. True or false, there is always a human story and the will to crucify begins to waver.

But what is to be done? However much we warn students of the dire consequences of plagiarism, some continue to take the risk, perhaps partly because the consequences tend not to be so dire after all. When I was an undergraduate there was an urban myth that anyone found committing plagiarism would be expelled and thereafter banned from all public exams in the land. But the truth is more often that all we can do is fail the piece of work in question. Often there is a right to resit next year, and so, like the House of Lords, all the plagiarism committee can do is to hold things up a bit.

Plagiarism doesn't look like going away on its own any time soon. The main response to this in the universities has been to turn to agencies that claim to be able to detect plagiarism by sophisticated electronic searches, if you give them enough money. Yet the plagiarists, if determined enough, will always be able to keep one step ahead of this year's software updates.

Another response has been to require students to keep a record of the "history of production" of their essays. Notes, early drafts, and records of meetings with tutors should all be kept on file to show how the final result was created. Reproducing such a file would be quite a challenge for a plagiarist. Yet this has a nasty smell: it seems to presume all are guilty unless they can prove themselves innocent.

There are other alternatives. It has been suggested that we might re-conceptualise the idea of essay writing and coursework. Should it matter if the student has not put things in his or her own words? After all, a question has been asked, and if an answer has been found, how much does it matter whether it has been copied out of a book? Probably quite a lot, actually. But we could at least start to think about this question. Or we could abolish coursework, and go back entirely to sit-down examinations. A retrograde step, some would say, but it would put the essay mills out of business, and that would be very satisfying indeed.

· Professor Jonathan Wolff is head of the philosophy department at University College London. His column appears monthly