March 3, 2021

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
  • Check out David’s website
• Host: Brett Hall
  • Check out Brett’s website
• 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

Tokcast : philosophy, physics, science
Notes By Giorgio Parlato