What is Knowledge?

Not too long after your China trip, you go to visit your best friend. She tells you that when your brain was reassembled in China, it was put in a jar and hooked up to a supercomputer which feeds electrical impulses into it simulating real sensory input. “But I’m standing here talking to you”, you say. “You’re right in front of me. I’m really here!” “I’m just a graphical image being fed into your brain”, she replies. “But it doesn’t really matter. I am just as good a friend as a real person. ” She smiles warmly.

“But it DOES matter! You’re my REAL best friend. I’m not just a brain in a jar!” “Prove it !”, your friend replies. You are starting to get angry. You are disappointed that your friend can’t just look into your eyes and tell that it is really you looking back, not just a brain in a jar. Your friend morphs into Christopher Walken, who winks at you. You wake up in a cold sweat.

An example Epistemological question: How can we distinguish dreams, illusions and hallucinations from genuine experiences ? Do genuine experiences have special characteristics that distinguish them from illusory experiences? Can we reason out the difference in terms of the coherence of the story the experiences tell? How would we apply these ideas to the brain in the jar hypothesis? What would show that the hypothesis was true or false? Can we directly perceive that an experience is genuine, without having to examine its qualities or reason things out?

Everything we know comes either directly or indirectly from sensory experience. We can only examine the qualities and characteristics of our perceptions and memories when we try to distinguish truth from illusion. If we have no perceptions or sensations of being in a jar, then we can safely assume that we are not in one. If our sensations are vivid and lifelike then we know we are awake and not dreaming.

A healthy mind can directly intuit the difference between a genuine experience and an illusory one. The genuine experience presents itself as authentic. Dreams, illusions and hallucinations do not. We could directly intuit the inauthentic quality of perceptions resulting from electrical inputs to our brain in the jar.

We use rational analysis of our perceptions to distinguish genuine from illusory experience. Are the experiences consistent with our theories and carefully reasoned out beliefs? Do they exhibit the order and regularity of phenomena governed by rational laws? We distinguish genuine from illusory experiences by examining their coherence, how well they fit in with our other expereinces, and with our beliefs and theories. If we could create experiences such as these by feeding electrical inputs into brains in jars, we would have succeeded in creating a new world for them to live in. Their experiences would be just as genuine as our own.

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