GREAT PROSPERITY begets psychic gloom. Never in human history have we been so secure, so wealthy, so free to follow our predilections. Yet our literature depicts a society on the edge of crisis, barely able to utter an optimistic thought or contemplate for a second that the future might be bright. We may be rich, it seems to be saying, but we're going to hell in a handcart.

A generation ago, Alvin Toffler scored a huge success with his book Future Shock. It suggested that life had become so headlong that human beings could not keep up. The rush of new technology was fostering alienation even as it created a world of comfort and ease. Toffler subsequently made a career out of propounding this dystopic vision, cheerily travelling from conference to conference making sure that nobody felt good about themselves.

While the details may change, this perception of the modern world has taken hold. Sue Palmer's Toxic Childhood suggested that a generation was growing up in circumstances as crippling, in their way, as the Victorian slums. Oliver James's Affluenza blamed rampant capitalism for giving us the blues. Now Susan Greenfield has written a book suggesting that our very identity as human beings is being threatened by the world we have made.

Her thesis is that a life lived vicariously in front of a screen is less enriching than one lived within the pages of a book. Children who watch TV, play computer games, rip off Wikipedia for prep and spend the few hours left to them texting their friends are going to be fundamentally altered.

Their lives will be lived in the here-and-now, dominated by short-term excitements and lacking the narrative and structure provided by a book. Since the brain is shaped by experience, she fears that the modern world is creating brains that will lack a context beyond the thrills and spills of a website and the short-term excitements of the virtual world. The best exemplars are the Japanese hikikomori - young men, predominantly, who have withdrawn from society and spend their time locked away in their rooms in symbiosis with a screen. There are said to be a million of them.

But ID is more than another lament for the passing of the book. It is an attempt to explain present discontents using what is known about how the brain functions. Yes, it's another book about the brain, skilfully disguised as an investigation into society's ills and the issue of identity.

It works best when Baroness Greenfield, a neuroscientist by profession, is on home ground arguing her own beliefs about the origins and possible treatments for Alzheimer's disease. She suggests that the brain cells vulnerable to degeneration in this awful illness originate in a different part of the embryo from other brain cells, and retain throughout life a sensitivity to the chemical agents that are important in development.

This could mean that degeneration is, perversely, a case of development going wrong. Damage to most parts of the brain by a stroke, a blow to the head, or normal wear and tear, is limited because the damage will not trigger further damage to neighbouring cells. But damage to the regions most inimately involved in Alzheimer's will spread. The cells will activate a mechanism involved in development that allows calcium to cross the cell walls, where it will gum up the inner workings of the cell, creating a spreading wave of damage.

This is a hypothesis in search of evidence. But it has the virtue that at least it is open to corroboration or disproof. Much of ID is so speculative that it lacks a banister to cling to; reading it is as disconcerting as hurtling downstairs unaided.

Lady Greenfield posits three types of identity. Those who are “Someone” locate themselves in relation to others, changing and responding as they gain experience. Those who are “Anyone” are characterised by action, not reflection, and have a more rigid caste of mind. Those who are “Nobody” are the hedonistic young, forever receptive to new stimuli but lacking the ability to assign any meaning to them. She fears that we are all becoming Nobodies.

In this nightmare world, the demarcation between individuals will become blurred as biotechnology is used to reshape faces closer to the desired ideal, and electronics obliterates the gap between the real and virtual worlds. Age will have no meaning as the limits on reproductive life are removed through IVF and genetic engineering. We will all look the same, think the same, and behave the same, bouncing unreflectively through life like a pinball in a penny arcade.

If I don't find this wholly persuasive, it is because I mistrust predictions of the future based on a snapshot of the present. Much of what Lady Greenfield says about reality TV, the decline of a shared culture, and the relative ignorance of the young are common currency among those of us in middle age. But to extrapolate this into despair at the disappearance of human individuality might be to stretch an idea beyond its natural limits.

Cheer up, chaps, things could be a lot worse. In almost all of human history, even to speculate about the future of human individuality would have been an outrageous indulgence, because it didn't exist. Let's reinvent H.G. Wells (the early version, not the author of Mind at the End of its Tether) and start feeling good about technology again.

iD: The Quest for Identity in the 21st Century by Susan Greenfield
Hodder & Stoughton, £16.99 Buy the book here

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