Tripartite Theory of Soul

Logical – Rational – logos
Spirited – Emotional – thymos
Appetitive – Physical Desires – epithymia

The Republic – Nature of Reality – Allegory of the Cave

René Descartes

Skeptic – a person who questions whether anything can be known with certainty

Cartesian Skepticism

Disbelieve everything

“All that up to the present time I have accepted as most true and certain I have learned either from the senses or through the senses; but it is sometimes proved to me that these senses are deceptive, and it is wiser not to trust entirely to anything by which we have once been deceived.”

Cogito, ergo sum or “I think, therefore I am.”

John Locke

Tabula rasa – blank slate

“Haven’t we already disposed of the difficulty about interaction involving a common element, when we said that mind is in a sense potentially whatever is thinkable, though actually it is nothing until it has thought? What it thinks must be in it just as characters may be said to be on a writing-tablet on which as yet nothing stands written: this is exactly what happens with mind.”

Distinction between Primary Qualities and Secondary Qualities

George Berkeley

(1) We perceive ordinary objects (houses, mountains, etc.).

(2) We perceive only ideas.


(3) Ordinary objects are ideas.

Esse est percipi – To be is to be perceived

Edmund Gettier

Is Justified True Belief Knowledge?

A subject S knows that a proposition P is true if and only if:

P is true, and
S believes that P is true, and
S is justified in believing that P is true

Gettier Cases – situations in which one can have justified true belief, but not knowledge

Karl Popper

“If we are uncritical we shall always find what we want: we shall look for, and find, confirmations, and we shall look away from, and not see, whatever might be dangerous to our pet theories.”

“In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.”

“…no matter how many instances of white swans we may have observed, this does not justify the conclusion that all swans are white”