Wednesday, March 13, 2013

"Scientific Proof" - an Idea Debunked

1. Let us find out what "scientific proof" really means
. . . and what it doesn't

     We can relate this to 
         daily life
         Earth 2100
         or whatever we feel like discussing

A starting point:
    What is the difference between

2. Math:
prove new things
based on
existing knowledge

Mathematical reasoning is:

  • 1+1=2
  • 2+2=4
  • Therefore,
    • 1+1+1+1=4
    • (proof by substitution)

  • All men are mortal
  • Socrates is a man
  • Therefore,
    • Socrates is mortal
    • (proof by "syllogism")

  • Deduction can prove things
  • Mathematics uses deduction
  • Therefore,
    • mathematics can prove things
    • (proof by syllogism again!)

3. Science is different from math!

  • Science is based on:
    • induction
    • (not deduction)
  • All apples that break off the tree,
    • fall down
  • Therefore, if I shake this apple tree,
    • and an apple breaks off,
    • it will fall down
  • Not a proof!
    • Can you think of a counterexample?

  • That which goes up has always come down
  • Therefore, if I throw this up, it will come down
  • Not a proof! Can you think of a counterexample?

4. Science needs more than induction

Humankind has always sought reasons

Scientists call those reasons
"theories" and "hypotheses"

Theories are the BIG ones
  • relativity
  • evolution
  • continental drift/plate tectonics

Hypotheses are the >little< ones
  • If the ground gets waterlogged,
    • water will get into my basement
  • IFSC majors 
    • are more employable 
    • than physics majors

Conclusion. . .
Math proves;
science does not prove!

Science disproves
(by refuting inductive "truths")

Science explains
(using theories)

Science predicts
(because the theories predict)

5. The phrase "scientific proof" makes no sense!
  • Science does not prove things!
  • It explains things and finds evidence
  • If only everyone actually knew that
  • Not just you, but also
    • reporters,
    • spokespeople,
    • politicians
    • the average person
6. Example: Global Warming

7. Example: Various medical advice

8. Example: US legal system

9. Example: More speculative science
                    ("Do toxoplasma germs control humanity?")

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