The law of reversal, as McLuhan calls it in his last book Laws of Media, recognizes an economic principle at work in the Logos (i.e. the 'reason and speech' of humankind).
McLuhan attributes this principle to Aquinas, who says that: 'in the preceding time, by which anything is moved towards a form, it is supported by its opposite form ...'1
McLuhan finds the same principle in the I Ching, 'that when any form reaches the end of its potential, it reverses its characteristics.'2
He elaborates in relation to the senses: 'to the degree that any situation is put in H[igh] D[efinition] ... that situation is at the point of drastic change and of the manifestation of opposite characteristics....'3
McLuhan also relates 'reversal' to the rhetorical technique of chiasmus, when '[t]wo statements of opposite intent are made at the same time'.4
Later, he aligns 'reversal' and chiasmus with Kenneth Boulding's concept of the 'break-boundary' in The Image, being the point at which 'the system suddenly changes into another or passes some point of no return in its dynamic processes.'5
Perhaps the most significant source of McLuhan's concept of reversal, however, is Teilhard's Phenomenon of Man.
For Teilhard, the Earth, and all its matter, is in a perpetual state of evolution, of 'genesis' (i.e. 'becoming'), so that, for example, there is no static form of the 'human being'; rather, a process of 'hominisation' (i.e. the becoming-human of the human being) is manifest in the species Homo Sapiens.
He conceptualizes the 'layers' of the Earth thus: barysphere (core), lithosphere (earth), hydrosphere (water), atmosphere (air), biosphere (organic matter), and 'noosphere' (thinking matter); later, he introduces the concept of the 'Christosphere', i.e. divine matter.6
Teilhard says that no form 'can go on increasing without sooner or later reaching a critical point involving some change of state'.7
A change of state, however, such as that of the birth of a consciousness that is aware of itself as such, 'does not represent merely a critical point that the individual or even the species must pass through. Vaster than that, it affects life itself in its organic totality, and consequently it marks a transformation affecting the state of the entire planet.'8
He explains: 'A continuous adjustment co-adapts [the forms of living matter] from without. A profound equilibrium gives them balance within. Taken in its totality, the living substance spread over the earth ... traces the lineaments of one single and gigantic organism.'9
Teilhard says that the phenomenon of 'consciousness', whether of the most rudimentary forms of interior perception or that of the human being, tells us that as well as a determinate exterior, or a 'without' to things, there must be also a 'free within'; and that 'the mind, seen from our side, is essentially the power of synthesis and organisation'.10
The evolution of a consciousness that is conscious of its role in the evolutionary process (i.e. that which is manifest in Hominisation), Teilhard interprets theologically, as a process towards an 'Omega Point' of consciousness, i.e. divinity.
Teilhard's argument in turn owes much to Bergson's theories on the evolution of consciousness. Commenting on Creative Evolution (1910), McLuhan says that for Bergson, 'consciousness is an extension of man that dims the bliss of union in the collective unconscious'.11
Bergson suggests that language is the means by which 'intelligence' is liberated: 'Without language, intelligence would probably have remained riveted to the material objects which it was interested in considering.... Language has greatly contributed to its liberation.'12
McLuhan summarizes: 'Speech acts to separate man from man, and mankind from the cosmic unconscious.'13
Meanwhile, McLuhan echoes Teilhard in regarding the advent of electronic communications technology as a 'prodigious biological event'.14
In 'The Formation of the Noosphere', originally published in 1947, Teilhard says that by means of electronic communications technology humanity is progressing towards an 'equilibrium' in which it is 'psychically centred upon itself'.15
He says that 'the whole of human history appears as a progress between two critical points: from the lowest point of elementary consciousness to the ultimate, noospherical point of Reflection....'16
Writing of 'the cosmic membrane that has been snapped round the globe by the electric dilation of our various senses', McLuhan explains that electronic communications technology form a 'central nervous system' for the planet, communicating information between all points of consciousness at the speed of light.17
McLuhan saw the computer as the ideal means for realizing a collective 'consciousness'.18
The subject does not cease to be 'conscious', i.e. to exercise his or her own senses and 'organizing' capacities; however, this role is subordinated to that of organ of the greater body (i.e. the 'Noosphere'), so that we witness a 'reversal' in role, from camera (i.e. conscious agent) to screen (i.e. agent for consciousness).
He comments upon the 'utter human docility' and 'servo-mechanistic fidelity' that such a role will require from its subjects.19
Yet he never says that the computer will replace consciousness; rather, 'a conscious computer would still be one that was an extension of our consciousness, as a telescope is an extension of our eyes, or as a ventriloquist's dummy is an extension of the ventriloquist.'20