ONE NIGHT about 20 years ago, I sat in a Toronto television studio expecting to conduct an interview with my friend Marshall McLuhan, and to moderate the ensuing discussion with a live audience. Five minutes before we were due to go on the air, the star had not yet arrived. We began the program without him. Then for 25 of the allotted 30 minutes the announcer was forced to interview me: "What are McLuhan's ideas about this?" and "What does McLuhan mean by that?" Marshall, the appointed taxi having sought him at the wrong address, arrived with less than five minutes to go, just in time to outer some entirely new inners.

The task of explicating the McLuhan mosaics has never been easy, even when it was serious fun. But for many of us, especially those working in the media, it has been essential to an understanding of our time, and will likely remain so for future students of our time, whether or not they approve of McLuhan's diagnostic method. One might have expected that with his death in 1980, followed by the publication of his letters last year, we would by now have the compleat text. No more revisions, only fresh interpretations. But now comes this half-posthumous volume, "by Marshall and Eric McLuhan," to further complicate the picture.

The complications are many and various.

The book, which Marshall began as a revision of Understanding Media, is now Laws of Media: The New Science. But the "laws" involved are general principles rather than binding injunctions ("The tetrad -- the four laws considered simultaneously, as a cluster -- is an instrument for revealing and predicting the dynamics of situations and innovations"). The "new" science, leaning heavily on the French sense of science as knowledge in general, is novel only in its rejection of the old rational "scientific method." Both are intended, moreover, to apply to more than the media. The discoverers found, says Eric in his introduction, that "they were applicable to the products of all human endeavour, and also to the endeavour itself! One colleague at the university tried them on remedies for cancer, and found they worked. With another, my father tried business procedures; with another, Newton's laws of motion. They worked! The flood-gates burst."

The difficulty is that in the ensuing inundation we have no means of knowing which McLuhan is the marshal. The introduction, the only part that is clearly Eric's, succeeds only in compounding the enigma.

'Me main thesis of the essays, whoever wrote them, is that all human endeavour can (no, must) be regarded as a "tetrad" -- a four-point process replacing the traditional "triad" of systematic thought, from Aristotle's syllogism through Hegel's dialectic to Koestler's triptych (though Koestler is unmentioned). The four-way process, we are told, reflects the bicameral structure of the mind, the delicate balance of which we have endangered by subjecting the right (intuitive, simultaneous) side to the left (rational, consecutive) side. These are clearly elaborations of Marshall's ideas -- as is the casting of himself in the role of corpus callosum, "the organ that facilitates interplay" between the two cerebral hemispheres; he earned it, and his elaborations should be worth study. "Be assured," begins Eric's introduction: "this is not just a rehashing of old fare dished up between new covers, but genuinely new food for thought and meditation." But who is the cook?

The operation began, apparently, with Marshall's files. With the help of a federal grant to Marshall, writes his son, "I was able to devote myself full time to assisting him during one crucial year (1979) when we extended the application of the laws to the arts and sciences. We found that everything man makes and does, every procedure, every style, every artefact, every poem, song, painting, gimmick, gadget, theory, technology -- every product of human effort -- manifested the same four dimensions. I don't consider it any exaggeration to say that confirming and detailing this tie, between speech and artefacts, constitutes the single biggest intellectual discovery not only of our time, but of at least the last couple of centuries."

Now Marshall was never a shrinking violet, but how did we get so quickly from "him" to "we" to "I," and from hypothesis to hyperbole? Who is responsible for what elaboration? Perhaps they're so closely inter-woven that generations of graduate students will make academic hay separating the hands of McLuhan pere et fils, in justifiable pursuit of the authorship of the biggest intellectual discovery of at least the last couple of centuries. But why has the surviving contributor not done it for us -- as, say, Alfano did when he completed Puccini's Turandot?

One could argue, I suppose, that differentiation does not matter as long as the collaboration works. The trouble is that sections of Laws of Media read like a parody of McLuhan, inviting us to see his summa summarum as self-caricature. He would not be the first genius to send himself up unintentionally -- he has been accused of it already -- but it would be helpful if we knew to what extent he has had it laid on him.

The question becomes even more urgent when one considers that much of the book contains a quite remarkable summation of Marshall McLuhan's themes. In particular, his important distinctions between visual (specific) and acoustic (resonant) space, between figure (selective) and ground (contextual), and between propositional and appositional statements, are here developed and expanded -- with telling implications for art, science, and the media ("subliminal ground- configurations"). His conception of art as an essential instrument is clarified ("It is the role of the artist to keep the community in conscious relation to the changing and hidden ground of its preferred objectives"), and his analysis of modern business, propaganda, and especially education ("a new biological stratagem") has never been sharper. But who, then, deserves the credit?

Left brain/right brain studies, as neurologists probe further, would seem to confirm many of McLuhan's earlier binary hypotheses -- figure/ground hot/cool, and the like. But now, we are confronted with an elaborate game of up by a surfeit of quotations from scholarly authorities with pedigrees more often weighty than relevant, in which two is squared into four and the answer proclaimed the only one applicable -- to every human endeavour. ("Once the number of laws is known -- and it will be four -- we can be certain that every human artefact will occasion those transformations.") We are offered 90 pages of sample tetrads, resembling concrete poems (visual verse about acoustic space?), proving mainly that lexicographers can have as much fun as you or I if they set their minds to it. Some of them are marvellously evocative -- but who wrote them?

Despite the introductory disclaimer, far too much time is spent expounding Marshall's once innovative but now widely adopted theses -- tools as human "extensions," for instance -- and not nearly enough explaining the stopper sentences that crop up everywhere as the probes are pushed further. The syllogism is described at some length, with elementary examples ("All As are Bs; C is an A; therefore C is a B") -- though why someone unfamiliar with it would choose to go beyond the first page of this book I have no idea -- while oddly yoked words and phrases that cry for an explanation go without one. In the very last paragraph, we get -- applied to the .tetrads, and for the first time -- vivisection, hologram, and psychic energies. Was the editor an accomplice in flimflam, or just too close to notice?

Such verbal shock tactics, of course, along with the attendant dogmatism, were Marshall's stock- in-trade. Trying to jolt us out of traditional patterns of thought, he delighted in using old words in unaccustomed ways, often going to great pains to justify the novel sense. He juggled with jokes and pedantry, street jargon and intellectual fireworks, always insisting on the validity of "manifold interpretation." But did his skill improve, his aim grow better, or -- as this book sometimes suggests -- wilder? Did Marshall's aphoristic, gnomic, witty, configurative style turn at the end into the pretentious rodomontade it was always on the edge of, or has Eric, in excessive emulation of his dad's chutzpah, pushed it over the brink?

In the urgent campaign to understand ourselves, Laws of Media, with all its baggage, is an important text. But I finished it in a cold sweat, such as I felt in that studio 20 years ago, wondering whether Marshall McLuhan would send in a substitute or, like Godot, not show up at all.