Introduction to Epistemology
Introduction to Epistemology 
Epistemology is the study and inquiry into the nature of knowledge and what we can know. The Ancient Greeks had notions about reality and knowledge. Plato's Allegory of the Cave was an early analogy to reality and the acquisition of radical knowledge. Throughout the years, philosophers have discussed the individual's relationship to reality and knowledge, and 'what we can know.'
Descartes' Meditations 
René Descartes' Meditations were an early foray into the field of epistemology and scepticism — questioning what a person can know. Descartes begins his work by relating reality to a dream, and wondering whether anything around him is truly real.
That is, he notes that, in a dream, the fire in his fireplace feels as warm as it does now. How does he know that he is simply not dreaming now, and all the time, and that reality is not an illusion? Descartes posits that there could be an "evil daemon" who is dedicated to fooling him, pulling the wool over his eyes and creating this false world for him to see.
Descartes, fairly early in the Mediations, concludes that firstly:
- Cogito ergo sum.
- I think, therefore I am.
He realizes that, even if he is being fooled about everything that is going on around him, he must still exist to be able to be fooled.
Brain in a jar 
Descartes' early scepticism has been reworked in a modern question: "How do I know that I am not just a brain in some mad scientist's lair?" Indeed, many sceptics would defend this thesis. But again, if you were in that unfortunate position, you would still have to be at least a brain.
Building up knowledge 
Descartes continued throughout his Meditations to build the foundations for mathematics and much of reality, to the point near the end where reality was, to him, everything he had perceived at first.
Gettier and Justified True Belief 
Until the late twentieth century, the epistemological community had settled comfortably into the belief that knowledge was "justified true belief." That is, if a person holds a true belief, and that is justified, he knows that fact.
For example: I believe that the car in my driveway is red, because I can see it through the window right now. [I am justified to believe that fact.] Therefore, I know that the car in my driveway is red.
Even if I held the belief that there are 85,486,075,000,000,000,000 gallons of water in the Atlantic Ocean, it would be difficult for me to know it. It may very well be true, but I would also have to be justified in my belief: I would have had to have some proof or some firsthand experience with the exact number of gallons of water in the Atlantic ocean in order for my belief to be justified.
This theory of knowledge known as justified true belief (JTB), was thrown into question when Professor Edmund Gettier published a three page paper on the occassion of his review for tenure.
Try this!: Pinch me 
Can you tell the difference between a dream and reality? Think of relevant disanalogies between the two. For example:
- In a dream, there seems to be a lack of logical progression of events
- In a dream, the traditional laws of physics are sometimes broken
- In a dream, I can fly if I try very hard, or I can instigate other events with thought
Take turns with a partner playing Devil's advocate and defending Descartes' original sceptical position.
Additional Reading 
- An Epistemological Nightmare, Raymond Smullyan, 1982.