I think McGilchrist's diagnosis of left brain hegemony is perfectly accurate -- as far as it goes -- but it's a little like Gorbachev's attempt to reform communism from within communism. Once you recognize the essential flaws of communism, the whole thing falls apart.
Even before getting into pathology -- i.e., diagnosis -- we must have a norm. In the absence of a norm, there can be no deviations, no perversion, inversions, regressions, or developmental arrests; nor can there be any meaningful evolution or development.
The function of the mind is to know reality. Thus, everything follows from the two principles embedded in this statement: first, that reality exists; and second, that we may know the truth of it.
The whole "modern turn" in philosophy, beginning with Kant, undermines these principles. It either denies one side at the expense of the other (as in scientism); or conflates them (as in the Chopraesque newage sewage of "perception is reality").
The result is, on the one hand, a desolate scientism that presumes to know the truth of reality, but without anyone to know it; or, a psychic projection of the nervous system. Thus, the world is either a left-brain scheme or a right-brain dream.
To his credit, McGilchrist is sensitive to this problem, but in the absence of a proper norm, he cannot propose a rigorous solution. Instead, he deals with the problem of left-brain tyranny on pragmatic grounds. He essentially says that the left brain has made a mess of things, so we need to rely more on the right.
He writes of, for example, "the profound kinship" between modernism and Nazism. But do we need to know about neurology to tell us that fascism is evil? Or in other words, is fascism what we call "evil" just because it involves a subjugation of the right brain by the left?
Of the "modernist enterprise," he writes that it involves a left-brain "admiration for what is powerful rather than beautiful, a sense of alienated objectivity rather than engagement or empathy, and an almost dogmatic trampling on all taboos..."
But with no norm other than utility, who's to say they're wrong?
The last chapter of the book is called The Master Betrayed (the master being the right brain). In it he presents a picture of what the world of the left hemisphere would look like, and it looks awfully familiar:
"We could expect, for a start, that there would be a loss of the broader picture, and a substitution of a more narrowly focussed, restricted, but detailed, view of the world..."
"The broader picture would in any case be disregarded, because it would lack the appearance of clarity and certainty which the left hemisphere craves."
"Ever more narrowly focussed attention would lead to an increasing specialization and technicalising of knowledge."
This "would promote the substitution of information... for knowledge, which comes through experience."
Knowledge "would seem more 'real' than what one might call wisdom, which would seem too nebulous..."
"There would be an increase in both abstraction and reification..."
Or, you could just say that the world becomes quantified at the expense of its prior -- and immediate -- qualities.
As a result, "the impersonal world would come to replace the personal..." "Individualities would be ironed out and identification would be by categories: socioeconomic groups, races, sexes, and so on," leading to intergroup competition, resentment, and paranoia. In other words, OBAMA-BIDEN 2012 (not to mention Big Chief Affirmative Token).
"Reasonableness would be replaced by rationality," leading to "a complete failure of common sense." "Anger and aggressive behavior would become more evident in our social interactions," since empathy is located in the right brain. And we can also expect sex to become "explicit and omnipresent," since the real implicit power of sex is located in the right.
The left-brain government of such a left-brain sheeple "would seek total control -- it is an essential feature of the left hemisphere's take on the world that it can grasp it and control it."
Obamacare, the attempt to control the economy via manipulation of aggregate demand, regulation of the world economy under the pretext of controlling the weather, state-mandated redefinition of marriage -- each of these flows from a left-brain fantasy. Oh, and give us your guns, especially those of you who don't buy into the fantasy.
In short, "Individual liberty would be curtailed," and "panoptical control would become an end in itself." The aim would be "to increase the power of the state and diminish the status of the individual.... according to the left hemisphere's take on reality, individuals are simply interchangeable parts of a mechanistic system, a system it needs to control in the interests of efficiency."
People are reduced to the proverbial Bags of Wet Cement, to be shoved around by the state. The state would "play down individual responsibility, and the sense of individual responsibility would accordingly decline." Loss of the implicit structure of the right brain would bring with it a flood of explicit legislation to try to control behavior.
We would see a "loss of insight, coupled with unwillingness to take responsibility," and an "increasing passivisation and suggestibility." "A sense of [existential] nausea and boredom before life would likely lead to a craving for novelty and stimulation." And of course, "Religion would seem to be mere fantasy."
So, what's the real solution? Seems to me I've been blah-blah-blogging about it ad gnoseum for over seven years, and I have no idea how to summarize it. But it's still one cosmos under god, regardless of what the left brain thinks.