昔者庄周梦为蝴蝶，栩栩然蝴蝶也。自喻适志与！不知周也。俄然觉，则蘧蘧然周也。不知周之梦为蝴蝶与？蝴蝶之梦为周与？周与蝴蝶则必有分矣。此之谓物化。
- The 'Equivalence of Things' (齐物论) chapter of the Zhuangzi (庄子) (c. 3rd c. B.C.E.)
Once upon a time I, Zhuang Zhou (庄周), dreamt I was a butterfly.
Flapping my wings in true butterfly fashion, I was happy as could be, and I knew nothing of any person named Zhuang Zhou.
But suddenly I awakened, astonished to be Zhuang Zhou.
I still don't know whether as Zhuang Zhou I was dreaming I was a butterfly or whether as a butterfly I was dreaming I was Zhuang Zhou.
There ought to be a difference between Zhuang Zhou and a butterfly, but this is called the transformation of things.
- David K. Jordan translation (adapted)
Gettier's Challenge
Edmund Gettier
Skepsis is the Greek word for 'investigation'
There have been several Gettier-style challenges to the JTB or standard analysis of knowledge:
EXAMPLE 1 (Dharmottara, c. 770 C.E., cited in Nagel, 2014):
A fire has been lit to roast meat. The fire has not started sending up smoke
The smell of meat has attracted a cloud of insects. From a distance, an observer mistakes the dark swarm of insects above the horizon for smoke
∴ The observer has a justified true belief that there is a fire burning at that spot
However, this observer cannot be said to know that there is a fire burning in the distance
EXAMPLE 2 (Russell, 1948):
Alice looks at the clock on the tower she sees every day to check the time
The clock shows 4 o'clock and Alice forms the belief that it is 4 o'clock
However, the clock has stopped and it has been showing 4 o'clock for the past 12 hours
∴ Alice has a justified true belief that it is 4 o'clock
However, Alice cannot be said to know that it is 4 o'clock
In EXAMPLES 1 and 2, we have instances of justified true belief but we do not have instances of knowledge
∴ The JTB analysis of knowledge misfires
Edmund Gettier's (1963) 'Is Justified True Belief Knowledge?'
Here are Gettier's own examples that challenge the JTB analysis of knowledge:
EXAMPLE 3 (Gettier, 1963):
Smith and Jones have applied for a job
Suppose that Smith has strong evidence for (S1 ∧ S2), where:
S1: Jones is the man who will get the job;
S2: Jones has 10 coins in his pocket
Smith’s evidence for (S1 ∧ S2):
EVIDENCE 1: The president of the company has assured Smith that Jones will be selected for the job;
EVIDENCE 2: Smith had counted the coins in Jones's pocket a few minutes ago
S3: The man who will get the job has 10 coins in his pocket
S1 ∧ S2 ⊦ S3
Suppose further that, unknown to Smith, it is Smith rather than Jones who will get the job
Incidentally, Smith also has 10 coins in his pocket
∴ While S1 and S2 would be false, S3 would be true
∴ Smith would have a justified true belief that S3
However, Smith cannot be said to know that S3 is true
EXAMPLE 4 (Gettier, 1963):
Suppose that Smith has strong evidence for proposition S1:
S1: Jones owns a Ford
Smith’s evidence for S1:
EVIDENCE 1: Jones has at all times in the past within Smith's memory owned a car and always a Ford
EVIDENCE 2: Jones has just offered Smith a ride while driving a Ford
Suppose that Smith has another friend, Brown, of whose whereabouts he is totally ignorant
Smith selects 3 places at random and constructs 3 propositions:
S2: Brown is in Boston
S3: Brown is in Barcelona
S4: Brown is in Brest-Litovsk
Here are 3 disjunctive propositions:
(S1 ∨ S2), (S1 ∨ S3), and (S1 ∨ S4)
S1 ⊦ S1 ∨ S2
S1 ⊦ S1 ∨ S3
S1 ⊦ S1 ∨ S4
Suppose that Jones does not own a Ford but is rather driving a rented car
Suppose further that by sheer coincidence and unknown to Smith, Brown is in Barcelona
∴ Smith would have a justified true belief that (S1 ∨ S3) (viz. 'Either Jones owns a Ford or Brown is in Barcelona')
However, Smith does not know that (S1 ∨ S3) is true
As EXAMPLES 1-4 show, Gettier-type cases pose a problem (known as the Gettier problem) for the JTB analysis of knowledge
