Canada, Michael Kinsley has written, is a nation of assistant professors. BCE Chairman Jean de Grandpre seems to have flushed out a good many of them with a speech, carried in the weekly Financial Post, on Canada's universities, in which he was careless enough to say that perhaps academic tenure should be abolished.

''Tenure is a concept foreign to business in Canada,'' de Grandpre declared. Well, not completely foreign. Being chairman of a monopoly public utility must lie somewhere in the same territory. But the sentiment remains. Guaranteed lifetime employment protects the incompetent, subsidizes the lazy, and waterlogs faculty budgets. And oh, what a squabble of academics (the correct collective, I believe) descended on him then!  

The flurry of letters had not yet subsided when Prof. William Watson from McGill University, of which de Grandpre is chancellor, last week offered his own defence of tenure in his regular Friday column. Of course, Watson, who usually champions competition, admits his bias. But he isn't going to get off that lightly.

Tenure, he says, is not really a guarantee of employment. It just seems that way. Showing ''just cause'' for dismissal is about as easy as proving the existence of God. So after handing out tenure like combat issue to the teeming thousands of young academics in the 1960s, Canada's university system is now stuck with a lump of about 70% of its teaching staff lodged in the tenure stream.

Combined with the entry barrier of a more or less unobtainable PhD - the credentialist disease that has only latterly begun to infect Britain, where some of the best professors have only their BA - it is little wonder that more than four fifths of the budget of Canadian universities goes to salaries and benefits.

ACADEMIC FREEDON

It's true, as Watson says, that without the security of tenure, universities would have to pay higher salaries to attract good professors. The difference is, they'd be good professors. Offering permanent employment to the indolent is a rather bizarre sort of cheap-labor strategy.

The traditional argument for tenure, aside from tradition itself, is that it safeguards academic freedom. Without such protection, professors would be loath to teach or publish unpopular opinions, for fear of offending their employers. Long-term research offering little obvious benefit would be curtailed in favor of a steady flow of quick-and-dirty journal articles.

But even with tenure, full academic freedom does not exist. The professor who taught that the Holocaust never happened would be unlikely to be invited to join the faculty of any university in Canada. And without tenure, academic freedom need not disappear. We already have a natter of human rights commissions to oversee these things. Further protection could be written into fixed-term contracts.

But the surest safeguard is reputation. A university that made a habit of firing its McLuhans would scarcely attract the best professors or students. To the extent that universities must compete for both, this seems a better approach than giving universal immunity to the daring and the dull alike. Put it this way. Suppose I were to insist that to protect the integrity of this column, The Post would have to hire me for life. Think they'd accept my terms?

But the best is saved for last. ''Tenure's crucial to good hiring,'' Watson advises, given the specialization of scholarship. A professor of public finance is the only one qualified to judge another public finance professor's qualifications. Without tenure, he would hardly recommend the most talented competitor for his job.

Let's think about this for just a second. If another professor of public finance is to be hired, it means one of two things: either the department needs two public finance professors, in which case our tenured friend would have nothing to fear, or it is replacing an unsatisfactory incumbent - in which case tenure is clearly undesirable. In any event, it would seem unusual to consult the incompetent, not to say insensitive. There are lots of other possible sources of evaluation: the editorial boards of scholarly journals, for example.

Held up to the light, tenure comes more and more to resemble yet another of the anticompetitive restrictions by which the professions have fattened their incomes and puffed up their self-image. Doctors and lawyers offer equally solemn justifications for their cartel privileges.

But public authorities are finally beginning to question the ever-mounting demands of the health-care industry. Reformers are looking at ways to allocate current health resources more efficiently, and to dismantle some of the privileges of the providers. It is time the same attention was turned to education.