In the 1969 Counterblast McLuhan writes of the “total matrix of living relations”, the “primordial matrix”, from which humans via an “enormous effort of collective abstraction” can ‘disentangle’ a new understanding of discrete areas of life (such as geometry):

Geometry is visual space. An enormous effort of collective abstraction [as occurred in Greece 2500 years ago in the founding of geometry] precedes the disentangling of these [focal] elements from the total matrix of living relations. Today an even greater energy is needed (…) to understand in a connubium [in a complex singularity like a city], the unity of all the elements which men have abstracted by their codes from the primordial matrix. 

As regards the still un-dis-covered (or, at least, uncommunicated) field of human perception, this “total matrix” or “primordial matrix” is “the entire range of human personal expressiveness”¹, the “complete a range of expressiveness”², the “medium itself”³, from which any particular perception of an individual or a society may be regarded as abstracted. In this same sense, any sample of physical material may be studied as abstracted from the “total matrix” or “complete range” of chemical possibilities (which “range” or Mendeleev’s table is of course just what chemistry is).⁴

In the passages below, McLuhan points to this matrix or range of expressiveness that amounts to the spectrum of possibilities out of which human experience may be specified — and thereby investigated — as generated:

Technology and Political Change (1952)
If the new reality of our time is in the main a collective dream or nightmare brought about by the mechanization of speech (television takes the final step of mechanizing the expressiveness of the human figure and gesture) then we must learn the art of using all our wits in a dream world, as did James Joyce in FINNEGANS WAKE. 

Technology and Political Change (1952)
Seen as communication networks, all cultures past or present represent a uniquely valuable response to specific problems in interpersonal and inter-social communication. This position amounts to no more than saying that any known language possesses qualities of expressiveness not to be found in any other language [just as any sample of physical material must be investigated as a unique product of the elements composing it].

Notes on the Media as Art Forms (1954)
Andre Malraux came up with the news of ‘museums-without-walls’. The main force making in that direction he saw was the clarification of the painter’s medium itself. The canvas gradually freed from anecdote and narrative became in our time not a vehicle but sheer expression.

Notes on the Media as Art Forms (1954)
Every medium is in some sense a universal, pressing towards maximal realization. But its expressive pressures disturb existing balances and patterns in other media of culture. The increasing inclusiveness of our sense of such repercussions leads us today hopefully to investigate the possibilities of orchestral harmony in the multi-levelled drive towards pure human expressiveness.⁵

Historical Approach to the Media (1955)
Radio and TV were not just the electrification of speech and gesture but the electronification of the entire range of human personal expressiveness.

Nihilism Exposed (1955)
On the plane of applied science we have fashioned a Plotinian world-culture which implements the non-human and superhuman doctrines of neo-Platonic angelism to the point where the human dimension is obliterated by sensuality at one end of the spectrum, and by sheer abstraction at the other.

Educational Effects of Mass Media of Communication (1956)
If our new media constitute so complete a range of expressiveness as both to enhance and almost to supplant speech itself, then we have moved into the period of post-literacy. If our present means of exploring and presenting the human past are such as to make simultaneously present all kinds of human pasts, then we have moved into the period of post-history.

Prospect (1962)
The fact that we have many media now enables us to leap across the barriers from one form or one set of rules to another. And I think it is this multiplicity of media that is now enabling man to free himself from media for the first time in history. He has been the victim, the servo-mechanism of his technologies, his media from the beginning of time, but now because of the sheer multiplicity of them he is beginning to awaken.

Counterblast (1969)
Our craving today for balance and an end of ever accelerating change, may quite possibly point to the possibility thereof. But the obvious lesson of all this development for education seems to me both simple and startling. If our new media constitute so complete a range of expressiveness as both to enhance and almost to supplant speech itself, then we have moved into the period of post-literacy. If our present means of exploring and presenting the human past are such as to make simultaneously present all kinds of human pasts, then we have moved into the period of post-history. Not that we are to be deprived of books any more than of ancient manuscripts. But it is plain that our new culture is not going to lean very heavily on any one means of encoding experience or of representing reality.⁶