McLuhan interprets the Western tradition in light of the 'trivium', i.e. the ancient arts of grammar (Grammatica), the art of interpretation; rhetoric (Rhetorica), the art of eloquence or persuasion; and dialectic (Dialectica), the art of philosophy or logic.
The trivium, as taught in the medieval university, was roughly equivalent to an undergraduate degree, and served as foundation for study of the 'quadrivium' of arithmetic, astronomy, geometry, and music.
McLuhan stresses the connection, since ancient times, between grammar and science, i.e. the notion of 'Nature' as a 'book' to be read.
Grammar, McLuhan shows, was the established mode of science from Plato through until the twelfth century (alchemy, for example, was grammatical in method); in the thirteenth century the dialectical method of Aristotle won new adherents through the work of St. Thomas Aquinas.
McLuhan says that science since the Renaissance (in fact since Descartes, a dialectician par excellence) tends to be dialectical, however the grammatical tradition has not been eliminated entirely, persisting in the work of Charles Darwin, for example, and the dream interpretations of Sigmund Freud.
McLuhan's last book, Laws of Media: The New Science (1988), completed after McLuhan's death by his son Eric McLuhan, takes its subtitle from Francis Bacon's Novum Organum (New Instrument [for the interpretation of nature]), first published in 1620, and Giambattista Vico's Scienza Nuova (New Science), first published in 1725.1
There are and can only be two ways of searching into and discovering truth. The one flies from the senses and particulars to the most general axioms, and from these principles, the truth of which it takes for settled and immovable, proceeds to judgement ... And this way is now in fashion. The other derives axioms from the senses and from particulars, rising by a gradual and unbroken ascent, so that it arrives at the most general axioms last of all. This is the true way, but as yet untried.