Chapter 1 “The Reach of Explanations” | TokCast with Brett Hall

Key Takeaways

  • For most of the history of science, we mistakenly believed that we derive theories from our sensory experiences
    • While essential to science, experience is not the source of theories
    • Experience allows choosing between different theories that have already been guessed
  • Scientific theories are about reality, which is often different from anyone’s experience
    • Astrophysics is not about our experience of stars, but about what stars are
  • Karl Popper claimed (and most people agree) that for theories to be “scientific” they must be testable
    • But testability is not enough because prediction is not the purpose of science
      • If you predict the outcome of a magician’s trick (prediction is testable), it does not mean you understood the trick
  • The quest for “good explanations” is the basic principle of Science
    • A good explanation is hard to vary because all the details play a functional role
    • Good explanations are often simple or elegant (Occam’s razor)
  • Some explanations can solve problems beyond those that were created to solve
    • The theory reaches out from its finite origins in one human brain to infinity

Intro

  • TokCast (TOK=Theory of Knowledge) is a podcast about the work of David Deutsch
  • David Deutsch (@DavidDeutschOxf) is a British physicist known for pioneering the field of quantum computation, he also made important contributions in the fields of philosophy, economics, politics, mathematics, and more
  • Host: Brett Hall
  • In this episode, Brett reads and discusses some passages from the first chapter of David Deutsch’s book The Beginning of Infinity, “The Reach of Explanations”

Where Do Theories Come From?

  • For most of the history of science, we mistakenly believed that we derive theories from our sensory experiences
    • Making observations from Nature to derive knowledge
    • This is known as empiricism
      • Empiricism brought progress in science by denying the knowledge of priests and religions
  • In reality, scientific theories are not “written in Nature”, they are guesses created by human minds
    • While essential to science, experience is not the source of theories
    • Experience allows choosing between different theories that have already been guessed
  • Empiricism had not seriously been challenged until Karl Popper in the mid-1900s

Critiques to Empiricism and Inductivism

  • How can your experience about something help you derive knowledge about something you didn’t experience?
    • How can you learn about physics on Mars from experiments done on Earth?
  • To reach conclusions about what was not experienced, empiricism relied on inductivism
    • If you repeatedly have similar experiences under similar circumstances, you can predict that the pattern will continue
      • You expect the sun to rise tomorrow morning because you’ve seen it do so every day
  • Inductivism intends to create theories from experience
    • Yet, scientific theories are about reality, which is often different from anyone’s experience
      • Astrophysics is not about our experience of stars, but about what stars are
  • Inductive inferences tend to assume that the future will resemble the past (or the unseen resembles the seen)
    • In reality, the future is unlike the past
      • Science consistently creates phenomena that were never experienced before
      • Humans flying or nuclear bombs are examples
    • Even if you experience the same thing every day, you can’t be sure that it will be the same tomorrow
  • “Induction is irrationality, it is a way of generalizing” Brett Hall
    • Hasty generalization is a logical fallacy that relies on induction
      • This kind of faulty reasoning leads to racism

Justificationism, Fallibilism, and The Enlightenment

  • There is a misconception that knowledge “needs” authority to be genuine
    • This is known as Justificationism
      • For something to be true, it needs to be designated as true by a reliable authority
      • Instead of asking “How do we know”, it makes us ask “What authority says so”
  • The opposing position to Justificationism is called Fallibilism 
    • Since people, who are fallible, are constructing knowledge, we can never be sure that anyone found the perfect theory
  • Fallibilism is not just about the rejection of authority
  • The fact that you can be wrong, implies that there is an objective truth, but we can never be sure of it
    • Some theories have already been proven false
    • Objective progress is done by proving more theories false
    • Criticism of theories gets us closer to truth
  • The Enlightenment was a revolution in how people sought knowledge
    • People stopped relying on authority and developed a tradition of criticism

What Differentiates Science from Not-Science

  • Karl Popper claimed (and most people agree) that for theories to be “scientific” they must be testable
    • A scientific theory must make predictions that could be proven false
    • While scientific theories can’t be derived from experience they can be tested by experience
  • But, testability alone cannot be enough to demarcate science
    • Testable theories have always existed
      • Cavemen trying to make better weapons could have a theory and test it
  • Testability is not enough because prediction is not and cannot be the purpose of science
    • If you predict the outcome of a magician’s trick (prediction is testable), it does not mean you understood the trick
    • Science requires an explanation
      • Ancient Greeks used to correctly predict winter through the myth of the Goddess Persephone, going to the Underworld every six months
      • A totally different myth about another God could have also explained it
  • When different theories can be used equally to explain  a phenomenon, choosing one theory over the others is irrational
    • Even if they make testable predictions, they are not scientific, they are myths
  • The quest for “good explanations” is the basic principle of Science
    • “We should conclude that a particular thing is real if and only if it figures in our best explanation of something” David Deutsch
  • A good explanation is hard to vary because all the details play a functional role
    • In the axis tilt theory of the Earth, if you tilt the axis by more or less than what they are, the seasons would be different
    • Good explanations are also hard to find
      • The harder they are to find, the harder they are to vary once found
    • Good explanations are often simple or elegant (Occam’s razor)
      • Bad explanations often contain superfluous features or arbitrariness
      • Removing the superfluous leads to better explanations
  • Extremely good explanations are the ones that passed many stringent tests
    • That’s why testability is still an essential feature of Science

The Reach of Explanations

  • How can we know so much about unfamiliar aspects of reality?
  • Some explanations can solve problems beyond those that were created to solve
  • Example of the axis tilt theory
    • It was initially proposed to explain the changes in the Sun’s angle of elevation during each year
      • Then it also explained seasons, why tropical regions don’t have them and why the sun shines at midnight in polar regions
      • The theory makes predictions even about planets that we’ve never seen
    • The theory reaches out from its finite origins in one human brain to infinity
  • We only find out about an explanation’s reach after we have the explanation
    • It has nothing to do with induction or extrapolating a theory
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Notes By Giorgio Parlato

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