My book’s topic seems to me so obviously important that I figure a reader’s main question must be whether he can trust me to actually know something on it. As a result, potential readers should be especially interested to hear criticisms; where do reviewers think my book gets it wrong? And as the book draws on many disciplines, readers should be especially interested in expert criticism, i.e., reviewers who find fault in an area they know well. Let us consider the reviews so far.

Three reviews so far can be seen as “main stream media.” At the Financial Times, journalist Sarah O’Connor calls the book “alluring” and “fascinating”, but notes that not everyone will accept the premise that ems are possible or “that current economic and social theories will hold in this strange new world.” However, the closest she gets to direct criticism is:

Some of the forecasts seem old-fashioned, like the notion that male ems will prefer females with “signs of nurturing inclinations and fertility, such as youthful good looks” while females will prefer males with “signs of wealth and status”.

At the Guardian, journalist Zoe Williams uses the book to direct readers to her critical question: “In a world without work, how do we distribute resources?” At Reason, journalist Ronald Bailey calls the book “fascinating”, and summarizes it in detail, but doesn’t otherwise evaluate it, other than to note that “other futurists have projected other pathways” that the future might take.

There are 2.5 reviews at widely read blogs. Economist Tyler Cowen likes the book, but cares less about its official topic than its indirect uses, such as a “Straussian commentary on the world we actually live in” and “A reminder of how strange everything is.” Economist Bryan Caplan has posted half of a review, on “What’s Right in Robin Hanson’s The Age of Em”; his other shoe has yet to drop.

Psychiatrist Scott Alexander really likes and highly recommends the book, though he worries that it is not weird enough, and he thinks I overstate my case on prior futurist accuracy. Alexander assigns low moral value to the scenario I describe, even though he sees it as full of happy complex creatures. He fears it will get even worse, leading to ems who are only ever focused on their particular work task, with no mind-wandering, breaks from work, or socializing.

There are also five reviews at other blogs. (There are also three reviews at Goodreads, and one more at Amazon, which don’t mention author expertise or offer field-specific criticisms.)

Futurist and computational neuroscientist Anders Sandberg calls the book a “very rich synthesis of many ideas with a high density of fascinating arguments,” but warns “most readers will disagree with large parts of it” and “many elements presented as uncontroversial will be highly controversial.” He himself only complains that I put in “too little effort bolstering the plausibility” of the basic idea of an emulation, a topic to which he has devoted in much effort.

Education reformer Neerav Kingsland calls the book “worth reading” though he would have rather I had written more fiction. He questions our ability to foresee the results of changes this big, and he questions my prediction of low wages: “Perhaps it would become taboo to replicate yourself, akin to teenage pregnancy?”

Private investor Peter McCluskey calls the book “quite valuable” though he notes my key assumptions could end up being wrong. He wishes I would have estimated wages relative to suspense more precisely, though he felt I was borderline overconfident overall, and thought I devoted too much attention to topics like swearing, relative to topics like democracy.

Economist Peter St Onge says “The pacing is fast, chock-full of interesting ideas to play with .. Hanson has done a fantastic job.” But he sees me as “too pessimistic” because the cost to run an em is very low compared to the cost to maintain a human today, and he just can’t see marginal product of human-like labor falling that low, no matter how many workers there are.

Physicist Richard Jones, in contrast, to the above nine reviewers, criticizes just about everything but my physics. He has long criticized Eric Drexler’s efforts to apply principles of mechanical engineering to tiny chemical systems. On Age of Em, he says:

Mind uploading .. will not be possible any time soon .. The brain .. is not the product of design, it is the product of evolution, and for this reason we can’t expect there to be such a digital abstraction layer. .. It would need to incorporate a molecularly accurate model of brain development and plasticity. .. His argument is that our understanding of human nature and the operations of human societies .. is now sufficiently robust that .. meaningful predictions can be made about the character of the resulting post-human societies. I don’t find this enormously convincing. .. Hanson often is simply unable to make firm predictions; this is commendably even-handed, but somewhat undermines his broader argument. .. How do we know what forager values actually were? Very few forager societies survived in any form into historical times, .. and what we know about their values is mediated by the biases of the anthropologists and ethnographers that recorded them.

So according to Jones, we can’t trust anthropologists to describe foragers they’ve met, we can’t trust economics when tech changes society, and familiar design principles fail for understanding brains and tiny chemical systems. Apparently only his field, physics, can be trusted well outside current experience. In reply, I say I’d rather rely on experts in each field, relative to his generic skepticism. Brain scientists see familiar design principles as applying to brains, even when designed by evolution, economists see economics as applying to past and distant societies with different tech, and anthropologists think they can understand cultures they visit.

Regarding O’Connor concerns on old-fashioned mate preferences I cited a literature on that, and regarding Alexander’s zero-leisure fears the book cites a literature on max productivity breaks and vacations. Regarding Kingsland and St Onge hopes for high wages, I’ll note that though most of history before the industrial era, taboos against having kids didn’t prevent marginal productivity from typically being very low.

So far I’d say that reviews give readers reasons to suspect my emphasis is at times off, but not strong reasons to fear that Age of Em is so wrong as to be not worth reading. But more reviews are yet to come.