✶Explainer07:30
Simplicity is not prior to science, it is posterior
Naval raises the criteria people use to spot good explanations, including risky narrow predictions such as Einstein's starlight bending, and the preference for the simplest answer. Deutsch rejects the simplicity criterion as usually stated: you can only define simplicity once you already have a theory of physics, because what counts as a short program depends on how bits behave. Quantum computation changed exactly that, making previously complex things simple.
- Good explanations make risky, narrow predictions nobody would have anticipated
- Simplicity can only be measured relative to an existing theory of physics
- Quantum computation redefined which computations count as simple
- This undercuts Solomonoff induction, which assumes a fixed measure of program length
- Deutsch expects a future physics to shift the notion of complexity again
“so there is no scale of complexity or Simplicity that is prior to physics”
“Simplicity is not prior to science it's posterior”
#explanations#simplicity#quantum-computation#induction
✶Explainer12:30
Why Einstein did not throw Newton away
Naval asks how we can be getting closer to reality when Einstein removed the gravitational force that was central to Newton's explanation. Deutsch answers in two parts: the theories share a great deal, including the heliocentric picture and the claim that the Sun causes planetary motion, and more importantly Newton's theory contains the problems that Einstein's theory solves. Instantaneous gravity and the dark night sky were live problems inside Newton's system.
- Both theories say the Sun's presence causes the motion of the planets
- Curvature of space-time replaces force but keeps the causal role of the Sun's mass
- Newton's instantaneous action at a distance was recognised as a problem before Einstein
- Olbers' paradox, the black night sky, could only be patched ad hoc within Newton
- Newton in turn solved the problem in Kepler's theory that Galileo could not accept
“the influence is not a force it's a curvature of space-time but that curvature of space-time is caused by the mass of the Sun”
“Newton said that gravity travels instantaneously that was a problem which people recognized before Einstein”
#physics#scientific-progress#newton#einstein
✶Explainer23:30
How to work on foundations while rejecting foundationalism
Naval asks how Deutsch can go as deep as possible into foundations while opposing foundationalism. Deutsch answers with the relationship between physics and structural engineering: foundations explain why the higher level theories are as they are, but you cannot build a bridge out of Newton's theory. Christopher Wren succeeded partly by using Newtonian mechanics to decide pillar spacing rather than relying on a master builder's eye, yet nowhere in the Principia is there a suspension bridge.
- Foundational theories explain higher level theories, they do not replace them
- Wren used Newton to compute spacing instead of trusting a builder's eye
- Foundations also serve as a critic, ranking designs as better or worse
- The suspension bridge was invented later and is nowhere in Newton
- Newton's real contribution was unifying understanding across fields
“foundations are theories that explain why the higher level theories are as they are but you can't use Newton's Theory to build a bridge”
“nowhere in Newton's principia is there a picture of a suspension bridge”
#foundations#engineering#explanation#newton
✶Explainer25:30
Why the English Enlightenment produced change without revolution
Naval asks why so much came out of England, from Newton to Wren to Turing. Deutsch answers that the Enlightenment there was a rebellion against authority that was not utopian. Instead of abolishing the ruling structure and installing a final truth, reformers extended existing privileges to more and more classes of people, so an Englishman's home became his castle rather than only an aristocrat's. France and Germany reformed by abolishing, and inherited a tradition of utopian institution building.
- England's rebellion against authority framed problems as fixable, not as enemies to remove
- Parliament and property rights were widened rather than rebuilt
- Utopian reform writes rights down once and makes them hard to change
- Britain produced rapid change over centuries without sudden revolutions
- In the 1930s British fascism never won a single MP and faded on its own
“it was a rebellion against Authority but it was a non-utopian rebellion”
“it was reforms were all about abolishing things abolishing the Tyrant”
#enlightenment#britain#political-philosophy#institutions
✶Explainer30:30
The crystal of knowledge across the multiverse
Naval summarises the idea from The Fabric of Reality that ties together epistemology, computation, quantum physics and evolution: knowledge is a thing that causes itself to be replicated in its environment. Useful genes, ideas and inventions get copied, while noise does not, so knowledge should appear as a structure common across the multiverse while randomness differs. Deutsch pushes back on the practical payoff, because there is no limit to the size of error we can make, so a long-lived religion can look just like a theory heading towards truth.
- Knowledge is what causes itself to be copied: fire, adaptive genes, working inventions
- Junk DNA and noise differ across branches while knowledge is common to them
- A multiverse view would in principle show truth as what is shared
- Deutsch objects that error has no upper bound, so size is no guide to truth
- The single-universe version, judging by persuasiveness, fails for the same reason
“knowledge is a thing that causes itself to be replicated in the environment”
“there is no limit to the size of error we can make”
#multiverse#knowledge#evolution#fabric-of-reality