Book Review - Reasons and Persons

Categories: Book Review

Written on February 14, 2022

Science is good explanations. The significance of the Enlightenment. The multiverse theory of quantum physics. Optimism for the future and its enemies. Why First Past The Post is actually a great election system.

‘This is Earth. Not the eternal and only home of mankind, but only a starting point of an infinite adventure. All you need do is make the decision [to end your static society]. It is yours to make.’
[With that decision] came the end, the final end of Eternity.
- And the beginning of Infinity.
Isaac Asimov, The End of Eternity (1955)

The Beginning of Infinity by David Deutsch is about many things, but primarily the power of good explanations. Humanity’s ability to comprehend and seek out these explanations is what sets us apart from other species. And our ability to rapidly conjecture and criticize explanations is what sets modern society, since the Enlightenment, uniquely apart from civilizations of the past.

An entire political, moral, economic and intellectual culture - roughly what is now called ‘the West’ - grew around the values entailed by the quest for good explanations, such as tolerance of dissent, openness to change, distrust of dogmatism and authority, and the aspiration to progress both by individuals and for the culture as a whole.

Explanations have causal (predictive) power across space and time

Deutsch argues that science is the pursuit of these good explanations and that these explanations can only be found through trial and error in a society that values them. There are underlying causal processes that make up and determine our world and science is the methodology to unravel those processes. Not only does this explain phenomena in front of us but also generalize across space and time. We can accurately predict events into the future and in other galaxies. For example, no human has ever experienced a black hole but we know an incredible amount about them. How? Because we have developed rich theories of physics that enable us to make predictions about what we will see and test them with sophisticated measuring tools (that we have also built and know to trust thanks again to our harnessing of causality).

Deutsch uses the power of explanations as a source of optimism: anything within the laws of physics is possible with knowledge of the right explanations. Having heard this pitch, it may seem like good explanations are so obviously desirable human society will guarantee optimizing for their discovery. However, coming up with good explanations is incredibly difficult because it requires the constant rejection of previous ideas. Have to really try. Everything is conjecture and experience. Need to constantly test these.

Deutsch tries to answer the question of why it took until the Enlightenment for society to foster the necessary culture of conjecture and criticism that science - the discovery of explanations - could really take off. To first ground this cultural shift that occurred, the Royal Society of London, founded in 1660 (around the start of the Enlightenment) used the slogan:

Nullius in verba - take no one’s word for it

And there is this great Feynman quote:

“Science is what we have learned about how to keep from fooling ourselves” - Richard Feynman

Why did it take until the 17th century for this truth seeking to flourish? Deutsch makes it a tragedy that Enlightenment values, like flowers that bloom but quickly wither, failed to take root during the times of Athens in 200BC and Florence in 1400. If the Englightenment had started at either of these times, we would have accumulated so much more knowledge by the year 2022. This same regret is applied to Charles Babbage and Ada Lovelace’s Differential Engine and where computing and by proxy all science would be today if their vision had been successful.

The Enlightenment and Scientific Revolution was indeed a revolution mostly through fabillism where nothing could be taken for granted, authority was rejected and theories needed to have real explanatory power. Taking nothing for granted led to conjecture which is crucial for developing new theories. This combined with making them testable and having a continued culture of criticism led to science.


Problems beget Problems

Sapiens, by Noah Yuval Harari, points out that life was likely much better when humans were hunter gatherers than when they were farmers and ever since then we have been stuck in a race to the bottom coordination problem of ever greater productivity. Deutsch acknowledges the same with problems begetting problems:

… frame the growth of knowledge (all knowledge, not only scientific) as a continual transition from problems to better problems, rather than from problems to solutions or from theories to better theories.

However, as implied by the use of the word “better” he is still in favour of dynamic societies that continue innovating. This is because a society that optimizes for stasis by keeping things the same will eventually fall to entropy in the form of a natural disaster or be out competed. This is related to Seeing Like a State

I have often thought that the nature of science would be better understood if we called theories “misconceptions: from the outset, instead of only after we have discovered their successors. Thus we could say that Einstein’s Misconception of Gravity was an improvement on Newton’s Misconception.”

Enemies of Progress

The “Principle of Mediocrity” and “Spaceship Earth” are separate theories but at a high enough level they agree that there is a limit to the reach of humanity. In the former we are not that unique and the world is too complex for us to be able to understand it. In the latter we exist only because of our biosphere cocoon that we should respect and not go beyond, also cannot go beyond as we have not made it for ourselves, evolved into it and were lucky. If we reach too far argue we will fail or end in catastrophe.

The Principle of Mediocrity is wrong because we exist in a highly unique part of the universe. We are in a galaxy. There is a very high density of particles. We can create things that defy average physics with 2.7K being the lowest temperature and we can get to 1 billionth of a Kelvin.

Spaceship Earth fails to acknowledge that evolution is a blind and brutal idiot god and the only reason we are free of Malthus’s trap at least for now is because we have innovated out of it and can do so far faster with knowledge than with biological or cultural evolution. The only reason Earth is a spaceship is because of our knowledge.

The biosphere only ever achieves stability - and only temporarily at that - by continually neglecting, harming, disabling and killing individuals.

The power of knowledge to infinity. Things are either possible under the laws of nature or not. No ifs or buts. If we cant do something it must be because it is a law against it and this is then has an explanation. We can colonize the moon and create a massive space ship in the middle of nowhere in the universe. All we need is matter, energy, and evidence to generate more knowledge.

Infinite Hotel, everyone is close to the start. can fit infinite people. deal with trash using a Zeno paradox like setup. But cant have infinite regress. why the puppy disappears. there is no last room we are aware of.

Infinity is Weird

Deutsch has a delightful chapter on the counter-intuitiveness of infinity. The strangest thing is that there is no measure. This makes probabilities of events meaningless. This means that we can’t ask the question of why our world has stable physical constants that allow for our existence or anything to exist at all.

First Past The Post is better than you’ve been told

One of my favourite chapters was a defense of the First Past The Post (FPTP) voting system employed by, amongst other countries, the US and UK. FPTP gives each person a single vote to cast for a candidate and the candidate with the most votes wins. This system is very lossy, failing to capture many voter preferences accounted for by systems like ranked choice where a voter rank orders their preferences for each candidate. This results in FPTP killing off minority parties that voters can’t support due to fear of splitting the vote.

However, Deutsch argues for two benefits of FPTP:

  1. Minority parties can become king makers and dominate legislatures. For example, say Republicans and Democrats each have 49% of the vote and are split on an issue, the Made-Up-Party that has 2% of the legislature’s seats then gets to decide what happens, giving their supporters outsized power.
  2. Pluralistic legislatures struggle to make decisions and get anything done. Israel has one of the most proportional voting systems in the world and has had to disband its government and redo its elections … times now. By being unable to make decisions there is no trial and error that is crucial for political parties, and a nation, to ultimately progress. Elizer Yudkowsky has a saying that I am sure Deutsch would agree with: “Not all changes in belief lead to truth. But all truth comes from changes in belief”. It is better for one party to have a majority, execute on its vision that got it elected, see how this turns out, and then replace them with different ideas in the next election than to take no actions at all.

Deutsch’s perspective throughout the book is over long time horizons of human history. What matters are the underlying norms and processes for science and rationality to be conducted that any specific answers or solutions. With the right underlying motivations the knowledge and good explanations will accumulate in a matter of time.

Everettian Many Worlds explanation of quantum physics

In another chapter, Deutsch turns to his expertise in quantum physics by explaining the Everett many worlds interpretation. Some parts of this explanation I found hard to follow. However, my high level understanding is that all fundamental particles are constantly splitting into an infinite number of divergent future trajectories. If the difference in states of the world between any two branches is small enough, than with some probability they can collapse back together again to become one. This means that there is an entanglement can have interference where the worlds collapse back into one. It is for this reason that quantum computing is so difficult, the entanglement will expand to the point where it is too large and a collapse can’t happen. The system needs to be completely isolated such that nothign else is entangled. This phenomena is best explained by the … two mirror experiments. The silvered mirrors have a probability of letting a photon pass through them or reflect it. Firing a single photon it will take both of the paths at the same time.

When reading this section I thought that the many worlds interpretation is Frequentist between worlds and Bayesian within worlds. I mean this in the sense that Bayesian have uncertainty about their observations of the world – there is one world and uncertainty for what will happen in it. Meanwhile, frequentists believe have uncertainty about what world they live in to give a particular observation – there are many wolds with a deterministic event that will unfold and it is unclear which world they are in. Applied to the many worlds interpretation, there are many worlds out there as the Frequentists imagine, however, we happen to inhabit one of these worlds and we always will such that we should be uncertain what will happen next in our own world. I’d be curious if this perspective resonates with any other readers.

Deutsch tries to argue that the many worlds interpretation of quantum physics is the only one that makes sense and the field has failed to embrace it due to irrationality and politics. He claims that Niels Bohr through sophistry made it foolish to ask non empirical questions about why quantum physics works the way that it does and that the field has not recovered since. I am somewhat skeptical of what sounds like a strawman and would have liked to have gotten a steel man of theories that conflict with the many worlds.

Related Work and Epistemic Humility


Without acknowledging it, David Deutsch gives strong support for predictive processing (Chapter …), human’s unique symbolic reasoning capabilities (Chapter …), Western society’s WEIRDness (Western, Educated, Industrialized, Rich and Democratic) (Chapter …), and support for the rationality movement. Converging with so many other ideas I find compelling from a different, first principles approach was nice and I would definitely recommend reading the book.

At times, failing to acknowledge these richer and more focused sources like those hyperlinked above made me feel Deutsch was missing important details and I wish he acknowledged this lack of detail leaving topics more open ended and less definitive. This was the most frustrating for his chapters on the origins of creativity and why Europe colonized the rest of the world. On Europe colonizing the rest of the world rather than vice versa, Deutsch provides a compelling rebuttal to arguments that this was pre-determined due to resource disparities of the sort presented in Guns, Germs, and Steel. Deutsch argues that instead, it was European innovation and dynamic societies that fostered these ideas. However, his argument remains vague and would have been significantly bolstered by bringing in the sorts of arguments and evidence presented in The WEIRDest People in the World1.

Regarding the chapter on creativity, I would have agreed with most of what he said if he had replaced “creativity” with “symbolic reasoning” and brought in more of the scientific research presented in Symbolic Species.

On one hand Deutsch certainly can’t cover everything in his book so these omissions make sense. On the other hand, Deutsch could leave more oxygen for deeper explanations. However, in the grander context of his book this is also forgivable. This is because Deutsch argues throughout that the most important thing for society to continue flourishing is through discovering better explanations (science) and the only way this can happen is through fostering a culture of conjecture and criticism. He also highlights how many scientists today will shy away from conjecturing bold theories to shield themselves against critique. In firmly conjecturing ideas about creativity and European colonizers Deutsch is putting his own skin in the game and I am sure he would be delighted to have his ideas be debated and refined.

In this light, I recommend reading the first half of the book in full before being looser with finishing chapters in the later half that become hit and miss.


It is striking that all organisms share DNA, RNA, and codons. The genetic code evolved to be universal (or close to it) and then stopped evolving any further or improving upon itself.


  1. In a podcast with Tyler Cowen Deutsch also comes off as incredibly confident and dismissive in a way I disliked and Tyler also commented on in his year in review episode

Thanks to and Max Farrens for reading drafts of this piece. All remaining errors are mine and mine alone.