February 21, 2020

How do we know what we know?

Tell me…

  • Do you smoke? Is it healthy? Why?
  • Do you vaccine your child? Why?
  • Do you eat meat? Why?

Do you believe in …

  • Climate change
  • Ghosts
  • Germs
  • Fairies

Do you believe in the existence of…

  • Atoms
  • UFO’s carrying aliens
  • Santa Claus
  • Donald Trump

The source of truth

How do we know what we know

First approach: Perception

We see, we hear: Empirical Truth

We grasp the world with our 8 senses

  • Sense-Certainty
  • see to believe

But …

Are they parallel?

Which blue circle is bigger?

Which one is bigger

Which color is the dress?

Google “The Dress”, and watch “The Dress is Bloie”

How many colors

Are A and B the same color?

Black or white dots?

Do the lines cross?

Do they cross?

Is this a movie?

Does this move?

Does this move?

Does this move?

Does this move?

Does this move?

We cannot trust our senses

  • We can have optical illusions
  • Same for the other senses
    • put one hand in hot water, the other in cold water
    • then put both in warm water
  • Perception depends on our expectations
    • Have you ever seen someone that was not there?


We dream

Our mind cannot be trusted

  • When we dream, we don’t know that we are dreaming
  • We cannot trust our memory
    • False memories can be created. See for example the work of Elizabeth Loftus
    • We can experience Déjà vu (Google it)

See for instance: Michaelian Kourken “Confabulating, Misremembering, Relearning: The Simulation Theory of Memory and Unsuccessful Remembering”. Frontiers in Psychology 7 (2016) DOI 10.3389/fpsyg.2016.01857

We have Incomplete information

“The Earth is flat”

We have incomplete information

We only see part reality. Our experience is limited

  • Our friends are like us. It seems that everybody agrees with us
  • At our scale, the Earth is flat, the mountains do not change, and atoms do not exist
  • We only see our neighborhood of the network, where everybody looks like us

The Earth looks flat

  • Today some people believe that Earth is flat
  • Some people believe that old people believed the Earth is flat

Our senses can fool us

  • Optical illusions
  • Dreams
  • Incomplete information

Distrust of senses
The body is dirty, the soul is pure

Plan B: Rational view

Truth emerges from Reason

  • Aristotle
    • logic syllogism
  • Euclides
    • geometry
    • axioms
    • theorems


Rational thinking chemically pure

  • Feelings are not important, but truth feels good

  • Beauty is not important, but truth is beautiful

  • Abstraction disconnects from details

Separate Essence from Accident

But people can disagree…

  • It is common that philosophers disagree on their reasoning
    • They start from different hypotheses
    • They use the same words with different meanings
    • Their logic may not be solid

Mathematics solved this problem

At the cost of loosing contact with reality

Math is not about nature. It is all imaginary

Math only exists in our minds

Math is the ultimate Humanist discipline

Correct reasoning is hard

The priority of our organism is

  1. Survival
  2. Save energy

So fast and gut decisions are automatic

  • Most of the time we use the cheap intuitive system
  • Rational thinking (i.e. math) is not spontaneous

Instead of thinking, we “guess” or “ask someone else”

“Truth from authority”

Plan C

  • Medieval/feudal point of view
  • “Aristotle was the most intelligent man, he must be right”
  • Knowledge is in “The Books”
  • Catholic church was built on this premise

Political power liked it: justified power

Question: what about …?

  • Thomas Aquinas
  • Baghdad’s House of Wisdom

Research Question 1: The “official” history is from a European point of view.

What can we say from the Middle-East point of view?

Is rationality enough?

Extramission theory of vision?

  • A theory accepted by Plato, Euclides and others
  • The eyes emit a “gentle” fire that touches the objects we see
  • We need to mix with another fire to see
    • like the sun
    • or a campfire

Geocentric model of the planets

People believed that Earth was inside crystal spheres

  • Stars were in a steel sphere
  • When we find a fallen star, it is made of steel
  • common prefix: “sider”

Fire, earth, water and air

Four elements

All material is a mix of these four elements.
For example

  • Wood is made of fire and earth.
  • Burning wood separates the fire
  • leaving only earth (ash) behind

Humor theory

Excess or deficiency of any of four distinct bodily fluids (humors) influences temperament and health

  • Classic Greek, Roman, Persian and Indian (Ayurveda)
    • Blood, Yellow bile, Black bile, Phlegm
  • Hippocrates (born c. 460 B.C.E.)
  • Galen (b. 129C.E. Asia Minor)
  • Bloodletting used until the 19th century

Today: Conspiracy theories

  • Apollo moon landings were staged
  • Weather control
  • GMO research is fake

Today: Conspiracy theories

  • Roswell UFO incident
  • Area 51
  • Kennedy assassination
  • 9/11

Research Question 2

What other things are believed by smart people despite evidence on the contrary?

What Aristotle did not knew

The age of discoveries showed that the old books did not have all answers

  • What about America?
  • What about Australia?


Where is the Truth?

The Truth is Out There